| **Employee Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions**                  | 12 Months Ended |
|-------------------------------------------------------------------------------------------------|-----------------|
||
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Minimum participant age to elect                                                                |            |   |   | 40 years |
| Employer discretionary contribution amount                                                      | $ 22            | $ 22 | $ 19 |   |
| Requisite service period                                                                        | 3 years         |   |   |   |
| Actual return on plan assets                                                                    | 24.50%          | 11.40% |   |   |
| Pension plan assets at fair value                                                               | $ 397           | $ 357 | 354 |   |
| Maximum                                                                                         |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Matching contribution to defined contribution plan                                              | 6.00%           |   |   |   |
| Pension Plan                                                                                    |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Percentage of increase decrease in benefit obligations discount rate                            | 0.29%           |   |   |   |
| Change In Net Benefit Cost Discount Rate Assumption                                             | 0.72%           |   |   |   |
| Pension Plan | Maximum                                                                          |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Cash dividends paid (less than $1 million)                                                      | $ 1             | 1 |   |   |
| Supplemental Employee Retirement Plan                                                           |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Accrued employee benefit                                                                        | $ 9             | 10 |   |   |
| Percentage of increase decrease in benefit obligations discount rate                            | 0.38%           |   |   |   |
| Change In Net Benefit Cost Discount Rate Assumption                                             | 0.81%           |   |   |   |
| Expected contribution by employer during 2021                                                   | $ 6             |   |   |   |
| Top Hat Savings Plan - Mutual Funds and Common Equities                                         |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| CFC Top Hat Savings Plan                                                                        | 64              | 51 |   |   |
| Top Hat | Top Hat Savings Plan - Mutual Funds and Common Equities                               |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| CFC Top Hat Savings Plan                                                                        | 64              | 51 |   |   |
| Top Hat | Top Hat Savings Plan - Mutual Funds and Common Equities | Maximum                     |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Employer discretionary contribution amount                                                      | $ 1             | $ 1 | $ 1 |   |
| Defined Benefit Plan, Equity Securities, Common Stock, Employer, Related Party                  |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Pension plan assets, shares                                                                     | 202,337         | 202,337 |   |   |
| Pension plan assets, fair value                                                                 | $ 23            | $ 18 |   |   |
| Defined Benefit Plan, Equity Securities, Common Stock, Employer, Related Party | Employee Stock |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Pension plan assets, shares                                                                     |            | 29,776 |   |   |
| Equity Securities                                                                               |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 87.00%          |   |   |   |
| Pension plan assets at fair value                                                               | $ 332           | $ 266 |   |   |
| Equity Securities | Information Technology Sector                                               |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 32.00%          |   |   |   |
| Equity Securities | Financial Services Sector                                                   |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 20.00%          |   |   |   |
| Equity Securities | Healthcare Sector                                                           |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 13.00%          |   |   |   |
| Equity Securities | Industrial Sector                                                           |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 12.00%          |   |   |   |
| Equity Securities | All Remaining Sectors                                                       |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 10.00%          |   |   |   |
| Fixed Maturities                                                                                |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Pension plan assets at fair value                                                               | $ 49            | 60 |   |   |
| Fixed Maturities | United States Government                                                     |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 8.00%           |   |   |   |
| Pension plan assets at fair value                                                               | $ 31            | 31 |   |   |
| Fixed Maturities | Domestic Corporate Debt Securities                                           |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 3.00%           |   |   |   |
| Pension plan assets at fair value                                                               | $ 11            | 20 |   |   |
| Fixed Maturities | States, Municipalities and Political Subdivisions                            |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Allocation percentage of investments                                                            | 2.00%           |   |   |   |
| Pension plan assets at fair value                                                               | $ 7             | 9 |   |   |
| Cash and Cash Equivalents                                                                       |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans**                                |            |   |   |   |
| Pension plan assets at fair value                                                               | $ 16            | $ 31 |   |   |

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| - Definition
Age at which participants could elect to remain in the defined benefit plan as of August 31, 2008.
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| - Definition
Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them.
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| - Definition
Amount of employer security in which defined benefit plan asset is invested. Includes, but is not limited to, security issued or managed by related party of employer.
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| - Definition
Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.
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| - Definition
Number of shares of employer stock in which defined benefit plan asset is invested. Includes, but is not limited to, stock issued or managed by related party of employer.
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| - Definition
Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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Amount of discretionary contributions made by an employer to a defined contribution plan.
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Percentage employer matches of the employee's percentage contribution matched.
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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.
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Value of the other investment not readily marketable determined by management based upon fair value methods, including pricing of similar securities and valuation techniques, that was used to record the investment for financial reporting purposes.
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