|**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) for eligible associates with matching company contributions totaling$19 million,$18 millionand$16 millionduring the years2019,2018and2017, respectively. Associates who are not accruing benefits under the pension plan are eligible to receive the company match of up to6%of cash compensation. Participants vest in the company match for the 401(k) plan afterthree yearsof eligible service.We maintain a supplemental executive retirement plan (SERP) with a benefit obligation of$11 millionatyear-end2019and$10 millionat year-end2018, 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$45 millionand$34 millionatDecember 31, 2019and2018, respectively. Company matching contributions to the CFC Top Hat Savings Plan totaled approximately$1 millionfor the years2019,2018and2017, respectively.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 PlanSERP2019201820192018Discount rate3.40%4.34%3.33%4.25%Rate of compensation increase2.25-3.252.25-3.252.25-3.252.25-3.25To 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 decreased the rate from the prior year by0.94percentage points for the qualified pension plan and by0.92percentage 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, but at year-end 2019 the base table was also changed to reflect the Pri-2012 tables released in2019. The RP-2014 table projected generationally with Scale MP-2018 and Scale MP-2017 were used for the years2018and2017, 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 PlanSERP201920182017201920182017Discount rate4.34%3.73%4.30%4.25%3.61%4.10%Expected return on plan assets7.007.257.25n/an/an/aRate of compensation increase2.25-3.252.75-3.252.75-3.252.25-3.252.75-3.252.75-3.25The discount rate was increased by0.61percentage points for the qualified pension plan and0.64percentage points for the SERP due to market interest rate conditions at the beginning of2019. 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 with2019expectations 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 for2019was24.5%and for2018was negative1.7%. Our compensation increase assumptions in2019reflect 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 31,20192018Change in projected benefit obligation:Benefit obligation, January 1$318$351Service cost811Interest cost1313Actuarial loss (gain)45(19)Benefits paid(34)(38)Projected benefit obligation, December 31$350$318Change in plan assets:Fair value of plan assets, January 1$318$345Actual return on plan assets70(4)Employer contribution—15Benefits paid(34)(38)Fair value of plan assets, December 31$354$318Funded status, December 31$4$—Accumulated benefit obligation$327$297Our funded status improved for2019primarily due to higher returns on plan assets partially offset by actuarial losses from decreases in discount rates and assumed lump sum rates.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 31,20192018Pension amounts recognized in the consolidated balance sheets:Other assets$4$—Total$4$—Pension amounts recognized in accumulated other comprehensive income:Net actuarial loss$9$16Total$9$16Below 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 31,201920182017Net periodic benefit cost:Service cost$8$11$11Non-service costs (benefit):Interest cost131314Expected return on plan assets(20)(22)(21)Amortization of actuarial loss and prior service cost112Other121Net periodic benefit cost$3$5$7Other changes in plan assets and benefit obligations recognized in othercomprehensive income:Current year actuarial (gain) loss$(5)$7$(11)Amortization of actuarial loss(2)(3)(3)Total recognized in other comprehensive (income) loss$(7)$4$(14)Total recognized in net periodic benefit cost and other comprehensive(income) loss$(4)$9$(7)The2019amount recognized in net periodic benefit cost and other comprehensive income improved from2018largely due to changes in the actuarial gain resulting from increases 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$3 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 for2019,2018and2017.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, during2019we held approximately77%of our pension portfolio in domestic common equity investments. The remainder of the portfolio consisted of8%in states, municipalities and taxable political subdivisions fixed-maturity investments,8%in domestic corporate fixed-maturity investments and7%in United States government fixed maturity investments. Our common equity portfolio consisted of23%in the financial sector,21%in the information technology sector,13%in the healthcare sector,13%in the industrial sector, and11%in the consumer discretionary industrial sector at year-end2019. No additional sectors accounted for10%or more of our common equity portfolio balance at year-end2019.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, 2019and2018. There have been no transfers between Level 1 and Level 2 for the years endedDecember 31, 2019and2018. The following table shows the fair value hierarchy for those assets measured at fair value on a recurring basis atDecember 31, 2019and2018. Excluded from the table below is cash on hand of$17 millionand$32 millionatDecember 31, 2019and2018, respectively.(Dollars in millions)Quoted prices inactive markets foridentical assets (Level 1)Significant otherobservable inputs (Level 2)Significantunobservableinputs(Level 3)TotalAt December 31, 2019Fixed maturities, available for sale:States, municipalities and political subdivisions$—$25$—$25Corporate—27—27United States Government25——25Total fixed maturities, available for sale2552—77Common equities260——260Total$285$52$—$337At December 31, 2018Fixed maturities, available for sale:States, municipalities and political subdivisions$—$29$—$29Corporate—37—37United States Government5——5Total fixed maturities, available for sale566—71Common equities215——215Total$220$66$—$286Our pension plan assets included232,113shares of the company’s common stock at bothDecember 31, 2019and2018, which had a fair value of$24 millionand$18 millionatDecember 31, 2019and2018, respectively. The defined benefit pension plan did not purchase or sell any shares of our common stock during2019and2018. The company paid less than$1 millionin2019and2018in cash dividends on our common stock to the pension plan.We estimate$9 millionof benefit payments from the SERP during2020. We expect to make the following benefit payments for our qualified plan and SERP, reflecting expected future service:(Dollars in millions)Years ended December 31,202020212022202320242025 - 2029Expected future benefit payments$31$26$25$26$28$147
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                                                                                                                                                                                                                                                                                                                                                                                                                     
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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Discount rate                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  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