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Income Taxes (Significant components of the Company's deferred tax assets and liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Deferred Tax Assets: |  |
Property and casualty claim and claim adjustment expense reserves | $ 74 | $ 125
Unearned premium reserves | 142 | 206
Receivables | 15 | 27
Employee benefits | 154 | 272
Life settlement contracts |  | 56
Deferred retroactive reinsurance benefit | 68 | 117
Investment valuation differences | 0 | 0
Other assets | 105 | 148
Gross deferred tax assets | 558 | 951
Deferred Tax Liabilities: |  |
Investment valuation differences | 55 | 57
Deferred acquisition costs | 77 | 120
Net unrealized gains | 233 | 309
Other liabilities | 56 | 86
Gross deferred tax liabilities | 421 | 572
Net deferred tax asset | $ 137 | $ 379

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