Investments - Gross realized gains (losses) on sales of fixed income securities (Details) - Assets held for sale - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Schedule of Available for Sale Securities
Gross realized gains	$ 245	$ 435
Gross realized losses	$ (64)	$ (59)

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).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

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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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- Definition

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.

+ References

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