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Employment Benefit Plans Stock Compensation (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share-based compensation expense [Abstract] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | 4,000,000 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | 1,383,489 |  |
Share Based Compensation Arrangement Shares Available for Future Issuance at Target | 2,079,181 |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification |  | $ 0 |
Share-based Payment Arrangement, Expense | $ 12 | 12 | $ 4
Total stock-based compensation (after-tax) | 12 | 12 | 4
Other Labor-related Expenses | 0 | 1 | 2
Share-based Payment Arrangement, Option [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based Payment Arrangement, Expense | 0 | 0 | 0
Restricted Stock Units (RSUs) [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based Payment Arrangement, Expense | 4 | 6 | 2
Performance Shares [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based Payment Arrangement, Expense | 8 | 6 | 3
Ambac UK [Member] | Performance Shares [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Other Labor-related Expenses | 5 | 1 | $ 2
Retained Earnings [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based Payment Arrangement, Expense | $ 0 | $ 0 |

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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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