Fair Values of Assets and Liabilities (Level 3 rollforwards-Assets) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Corporate debt securities [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period		$ 731	$ 790	$ 735	$ 871
Total Gains (Losses) Included in Net Income				(1)	(1)
Total gains (losses) included in other comprehensive income (loss)		5	4	13	32
Purchases		7	21	13	35
Settlements		(7)	(35)	(24)	(157)
Balance, at the end of the period		736	780	736	780
Changes in unrealized gains (losses) in net income relating to assets held at the end of the period				(1)	(1)
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		5		13
Residential mortgage backed securities [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period		56	44	17	64
Total gains (losses) included in other comprehensive income (loss)				1
Purchases		1		39	27
Settlements			(2)		(3)
Transfers out of Level 3		(39)		(39)	(46)
Balance, at the end of the period		18	42	18	42
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period				1
Asset backed securities [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period		352	384	389	374
Total gains (losses) included in other comprehensive income (loss)		32	(3)	(5)	7
Transfers Into Level 3		14		14	10
Balance, at the end of the period		398	391	398	391
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		32		(5)
Total [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period		1,139	1,218	1,141	1,309
Total Gains (Losses) Included in Net Income	[1]			(1)	(1)
Total gains (losses) included in other comprehensive income (loss)		37	1	9	39
Purchases		8	21	52	62
Settlements		(7)	(37)	(24)	(160)
Transfers Into Level 3		14	10	14	10
Transfers out of Level 3		(39)		(39)	(46)
Balance, at the end of the period		1,152	$ 1,213	1,152	1,213
Changes in unrealized gains (losses) in net income relating to assets held at the end of the period	[1]			(1)	$ (1)
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		$ 37		$ 9

[1] Included in net investment income in the Consolidated Statements of Income.