| **Employee Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions**                             | 12 Months Ended |
|------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Minimum participant age to elect                                                                           |            |   |   | 40 years |
| Employer discretionary contribution amount (less than $1 million for 2016 in the CFC Top Hat Savings Plan) | $ 18            | $ 16 | $ 14 |   |
| Requisite service period                                                                                   | 3 years         |   |   |   |
| Actual return on plan assets                                                                               | 1.70%           | 17.40% |   |   |
| Amortization of actuarial loss                                                                             | $ 1             |   |   |   |
| Amortization of prior service cost less than $1 million                                                    | 1               |   |   |   |
| Pension plan assets at fair value                                                                          | $ 318           | $ 345 | 315 |   |
| Domestic Equity Securities                                                                                 |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 75.00%          |   |   |   |
| Domestic Equity Securities | Financial Services Sector                                                     |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 21.00%          |   |   |   |
| Domestic Equity Securities | Healthcare Sector                                                             |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 14.00%          |   |   |   |
| Domestic Equity Securities | Consumer Discretionary Sector                                                 |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 10.00%          |   |   |   |
| Domestic Equity Securities | All Remaining Sectors                                                         |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 10.00%          |   |   |   |
| States, Municipalities and Political Subdivisions                                                          |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 10.00%          |   |   |   |
| Domestic Corporate Debt Securities                                                                         |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 13.00%          |   |   |   |
| US Government Debt Securities [Member]                                                                     |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 2.00%           |   |   |   |
| Cash and Cash Equivalents                                                                                  |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Pension plan assets at fair value                                                                          | $ 32            | $ 18 |   |   |
| Maximum                                                                                                    |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Matching contribution to defined contribution plan                                                         | 6.00%           |   |   |   |
| Pension Plan                                                                                               |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Percentage of increase decrease in discount rate                                                           | 0.57%           |   |   |   |
| Pension plan assets, shares                                                                                | 232,113         | 232,113 |   |   |
| Pension plan assets, fair value                                                                            | $ 18            | $ 17 |   |   |
| Cash dividends paid (less than $1 million for 2018)                                                        | $ 1             | 1 |   |   |
| Pension Plan | Benefit Obligations                                                                         |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Percentage of increase decrease in discount rate                                                           | 0.61%           |   |   |   |
| Supplemental Employee Retirement Plan                                                                      |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Accrued employee benefit                                                                                   | $ 10            | 9 |   |   |
| Percentage of increase decrease in discount rate                                                           | 0.49%           |   |   |   |
| Expected contribution by employer during 2018                                                              | $ 4             |   |   |   |
| Supplemental Employee Retirement Plan | Benefit Obligations                                                |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Percentage of increase decrease in discount rate                                                           | 0.64%           |   |   |   |
| Top Hat Savings Plan - Mutual Funds and Common Equities                                                    |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| CFC Top Hat Savings Plan                                                                                   | $ 34            | 31 |   |   |
| Top Hat | Top Hat Savings Plan - Mutual Funds and Common Equities                                          |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Employer discretionary contribution amount (less than $1 million for 2016 in the CFC Top Hat Savings Plan) |            | 1 | $ 1 |   |
| CFC Top Hat Savings Plan                                                                                   | $ 34            | $ 31 |   |   |
| Information Technology Sector | Domestic Equity Securities                                                 |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 20.00%          |   |   |   |
| Industrial Sector | Domestic Equity Securities                                                             |            |   |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block**                          |            |   |   |   |
| Allocation percentage of investments                                                                       | 11.00%          |   |   |   |

| X                                                                                                                                                                                                                                                  |
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Change in discount rate assumption.
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| - Definition
Defined Benefit Plan, Actual Percentage Return On Plan Assets
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| X                                                                                                                                                                                                                                                                                                                     |
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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
Defined Contribution Plan, Requisite Service Period
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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.
+ References
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| - Definition
The amount of employer securities or securities of parties related to the employer that are included in plan assets.
+ References
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| - Definition
Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.
+ References
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| - Definition
Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.
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| - Definition
Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.
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| - Definition
Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.
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| - Definition
The number of employer shares or related party shares included in plan assets.
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| - Definition
Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.
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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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| - Definition
Amount of discretionary contributions made by an employer to a defined contribution plan.
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| - Definition
Percentage employer matches of the employee's percentage contribution matched.
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| - Definition
Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.
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| - Definition
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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