Statement of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	$ (426)	$ (647)	$ 338
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	(36)	0	(41)
Net unrealized appreciation on investments, Change in year, income tax (expense) benefit	(462)	(647)	297
Cumulative translation adjustment, Change in year, income tax(expense) benefit	(4)	24	35
Pension liability adjustment, Change in year, income tax (expense) benefit	$ 50	$ 18	$ 67

Amount, before adjustment, of tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

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Amount, after adjustment, of tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References

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Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income of defined benefit plan.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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