Investments - Realized capital gains and losses by transaction type (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments [Abstract]
Sales		$ 1,017	$ 575	$ (215)
Credit losses		(80)	(47)	(14)
Valuation of equity investments		366	1,372	(691)
Valuation and settlements of derivative instruments		53	(15)	43
Realized capital gains (losses)	$ 4	1,356	1,885	(877)
Fixed income and equity securities
Schedule of Available for Sale Securities
Gross realized gains		1,209	607	120
Gross realized losses		$ (221)	$ (132)	$ (347)

Allowance for Credit Loss, Credit Loss Recognized In Net Income

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of unrealized and realized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity), investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
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-Name Accounting Standards Codification
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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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Amount of realized gain (loss) on investment.

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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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