Fair Value Measurements - Changes in Level 3 Financial Assets and Financial Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Transfers into/(out of) Level 3
Change in unrealized gains or losses included in other comprehensive income for assets held at the end of the reporting period	$ 17		$ (37)
Debt and Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance	860	$ 431	555	$ 410
Total gains (losses) included in shareholders’ net income	(1)	(6)	4	(7)
Gains (losses) included in other comprehensive income	17	4	(42)	16
Gains (losses) required to adjust future policy benefits for settlement annuities	7	1	4	3
Purchases, sales and settlements
Purchases	3	10	67	53
Sales	(1)	0	(13)	0
Settlements	(8)	(6)	(15)	(16)
Total purchases, sales and settlements	(6)	4	39	37
Transfers into/(out of) Level 3
Transfers into Level 3	102	80	629	113
Transfers out of Level 3	(33)	0	(243)	(58)
Total transfers into/(out of) Level 3	69	80	386	55
Balance	946	514	946	514
Total gains (losses) included in shareholders’ net income attributable to instruments held at the reporting date	$ 0	$ (6)	$ (2)	$ (8)