|**Employee Retirement Benefits**                                                              | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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|**Retirement Benefits [Abstract]**                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Employee Retirement Benefits                                                                  | Employee Retirement BenefitsWe sponsor a qualified defined benefit pension plan that we closed entry into for new associates as of June 30, 2008, and only participants40years of age or older as of August 31, 2008, could elect to continue to participate. During 2008, we changed the form of retirement benefit we offer some associates to a company match on contributions to a 401(k) plan as further explained below. For participants remaining in the pension plan, we continue to fund future benefit obligations. Benefits for the defined benefit pension plan are based on years of credited service and compensation level. Contributions are based on the prescribed method defined in the Pension Protection Act. Our net periodic benefit cost is based on certain actuarial assumptions and also is composed of several components that are determined using the projected unit credit actuarial cost method. The qualified plan has been amended to allow for distribution of vested balances to terminated participants.We sponsor a defined contribution plan (401(k) plan) with matching company contributions totaling$18 million,$16 millionand$14 millionduring the years2018,2017and2016, respectively. Associates who are not accruing benefits under the pension plan are eligible to receive the company match of up to6 percentof cash compensation. Participants vest in the company match for the 401(k) plan afterthreeyears of eligible service.We maintain a supplemental executive retirement plan (SERP) with a benefit obligation of$10 millionatyear-end2018and$9 millionat year-end2017, which is included in the projected benefit obligation. The company also makes available to a select group of associates the CFC Top Hat Savings Plan, a nonqualified deferred compensation plan, which had a fair value of$34 millionand$31 millionatDecember 31, 2018and2017, respectively. Company matching contributions to the CFC Top Hat Savings Plan totaled$1 millionfor the years 2018 and 2017 and less than$1 millionfor the year 2016.Defined Benefit Pension Plan AssumptionsWe evaluate our pension plan assumptions annually and update them as necessary. This is a summary of the weighted-average assumptions used to determine our benefit obligations at December 31 for the plans:Qualified Pension PlanSERP2018201720182017Discount rate4.34%3.73%4.25%3.61%Rate of compensation increase2.25-3.252.75-3.252.25-3.252.75-3.25To determine the discount rate for each plan, a theoretical settlement portfolio of high-quality rated corporate bonds was chosen to provide payments approximately matching the plan’s projected benefit payments. A single interest rate for each plan was determined resulting in a discounted value of the plan's benefit payments that equates to the market value of the selected bonds. The discount rate is reflective of current market interest rate conditions and our plan's liability characteristics. Based on this analysis, we increased the rate from the prior year by0.61percentage points for the qualified pension plan and by0.64percentage points for the SERP. Compensation increase assumptions reflect anticipated rates of inflation, real return on wage growth and merit and promotional increases. The mortality assumption is updated annually to reflect the updated scale. The RP-2014 Employee Mortality Tables and RP-2014 Annuitant Mortality Tables for males and females projected generationally with Scale MP-2018, Scale MP-2017 and Scale MP-2016 were used for the years 2018, 2017 and 2016, respectively. The updated mortality table did not have a significant impact on our consolidated financial statements as our qualified plan assumes the majority of benefits will be paid in the form of lump sums.This is a summary of the weighted-average assumptions used to determine our net periodic benefit cost for the plans:Qualified Pension PlanSERP201820172016201820172016Discount rate3.73%4.30%4.55%3.61%4.10%4.30%Expected return on plan assets7.257.257.25n/an/an/aRate of compensation increase2.75-3.252.75-3.252.75-3.252.75-3.252.75-3.252.75-3.25The discount rate was decreased by0.57percentage points for the qualified pension plan and0.49percentage points for the SERP due to market interest rate conditions at the beginning of2018. The discount rate assumptions for our benefit obligation generally track with high-quality rated corporate bond yields chosen in our theoretical settlement portfolio, and yearly adjustments reflect any changes to those bond yields. We believe the expected return on plan assets is representative of the expected long-term rate of return on these assets, which is consistent with2018expectations of interest rates and based partially on the fact that the plan’s common stock holdings pay dividends. We review historical actual return on plan assets when determining our expected long-term rate of return. Total portfolio return for2018was negative1.7percent and for2017was17.4percent. Our compensation increase assumptions in2018reflect anticipated rates of inflation, real return on wage growth and merit and promotional increases.Benefit obligation activity using an actuarial measurement date for our qualified pension plan and SERP at December 31 follows:(Dollars in millions)At December 31,20182017Change in projected benefit obligation:Benefit obligation, January 1$351$340Service cost1111Interest cost1314Actuarial (gain) loss(19)20Benefits paid(38)(34)Projected benefit obligation, December 31$318$351Change in plan assets:Fair value of plan assets, January 1$345$315Actual return on plan assets(4)52Employer contribution1512Benefits paid(38)(34)Fair value of plan assets, December 31$318$345Funded status, December 31$—$(6)Accumulated benefit obligation$297$322Our funded status improved for2018primarily due to actuarial gains from increases in discount rates and assumed lump sum rates partially offset by lower returns on plan assets.A reconciliation follows of the funded status for our qualified plan and SERP at the end of the measurement period to the amounts recognized in the consolidated balance sheets at December 31:(Dollars in millions)At December 31,20182017Pension amounts recognized in the consolidated balance sheets:Other liabilities$—$(6)Total$—$(6)Pension amounts recognized in accumulated other comprehensive income:Net actuarial loss$16$12Prior service cost——Total$16$12Below are the components of our net periodic benefit cost, as well as other changes in plan assets and benefit obligations recognized in other comprehensive income for our qualified plan and SERP at December 31:(Dollars in millions)Years ended December 31,201820172016Net periodic benefit cost:Service cost$11$11$11Non-service costs (benefit):Interest cost131414Expected return on plan assets(22)(21)(19)Amortization of actuarial loss and prior service cost123Other21—Net periodic benefit cost$5$7$9Other changes in plan assets and benefit obligations recognized in othercomprehensive income:Current year actuarial (gain) loss$7$(11)$(13)Amortization of actuarial loss(3)(3)(2)Amortization of prior service cost——(1)Total recognized in other comprehensive (income) loss$4$(14)$(16)Total recognized in net periodic benefit cost and other comprehensive(income) loss$9$(7)$(7)The 2018 amount recognized in net periodic benefit cost and other comprehensive income increased from 2017.The 2018 change in the amount recognized in other comprehensive income from 2017 is largely due to changes in the actuarial loss resulting from decreases in discount and assumed lump sum rates. The estimated costs to be amortized from AOCI into net periodic benefit cost over the next year for our plans are$1 millionin actuarial loss and less than$1 millionin prior service cost.Service costs and non-service costs (benefit) are allocated in the same proportion primarily to underwriting, acquisition and insurance expenses line item with the remainder allocated to the insurance losses and contract holders' benefits line item on the consolidated statements of income for 2018, 2017 and 2016.Defined Benefit Pension Plan AssetsThe pension plan assets are managed to maximize total return over the long term while providing sufficient liquidity and current return to satisfy the cash flow requirements of the plan. The plan’s day-to-day investment decisions are managed by our internal investment department; however, overall investment strategies are discussed with our employee benefits committee. Our investment strategy is to weight our portfolio towards large-cap, high-quality, dividend-growing equities that we have historically favored. As our plan matures and interest rates normalize, we expect a greater allocation to fixed-income securities to better align asset and liability market risks. Our fixed-maturity bond portfolio is investment grade. The plan does not engage in derivative transactions.Excluding cash, during2018we held approximately75 percentof our pension portfolio in domestic common equity investments. The remainder of the portfolio consisted of10 percentin states, municipalities and taxable political subdivisions fixed-maturity investments,13 percentin domestic corporate fixed-maturity investments and2 percentin United States government. Our common equity portfolio consisted of21 percentin the financial sector,20 percentin the information technology sector,14 percentin the healthcare sector,11 percentin the industrial sector and10 percentin the consumer discretionary industrial sector at year-end2018. No additional sectors accounted for10 percentor more of our common equity portfolio balance at year-end2018.Investments in securities are valued based on the fair value hierarchy outlined in Note 3, Fair Value Measurements. The pension plan did not have any liabilities carried at fair value during the years endedDecember 31, 2018and2017. There have been no transfers between Level 1 and Level 2 for the years endedDecember 31, 2018and2017. The following table shows the fair value hierarchy for those assets measured at fair value on a recurring basis atDecember 31, 2018and2017. Excluded from the table below is cash on hand of$32 millionand$18 millionatDecember 31, 2018and2017, respectively.(Dollars in millions)Quoted prices inactive markets foridentical assets (Level 1)Significant otherobservable inputs (Level 2)Significantunobservableinputs(Level 3)TotalAt December 31, 2018Fixed maturities, available for sale:States, municipalities and political subdivisions$—$29$—$29Corporate—37—37United States Government5——5Total fixed maturities, available for sale566—71Common equities215——215Total$220$66$—$286At December 31, 2017Fixed maturities, available for sale:States, municipalities and political subdivisions$—$31$—$31Corporate—34—34Total fixed maturities, available for sale—65—65Common equities, available for sale262——262Total$262$65$—$327Our pension plan assets included232,113shares of the company’s common stock at bothDecember 31, 2018and2017, which had a fair value of$18 millionand$17 millionatDecember 31, 2018and2017, respectively. The defined benefit pension plan did not purchase or sell any shares of our common stock during2018and2017. The company paid less than$1 millionin2018and$1 millionin2017in cash dividends on our common stock to the pension plan.We estimate$4 millionof benefit payments from the SERP during2019. We expect to make the following benefit payments for our qualified plan and SERP, reflecting expected future service:(Dollars in millions)Years ended December 31,201920202021202220232024 - 2028Expected future benefit payments$43$23$22$21$22$140
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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Discount rate                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Rate of compensation increase                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Discount rate                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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