Fair Values of Assets and Liabilities (Level 3 rollforwards-Assets) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2020		Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
Total [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		$ 67
Asset-backed Securities
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		52
Residential mortgage backed securities [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		1
Corporate debt securities [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Change in unrealized gains (losses) in OCI relating to assets held at the end of the period		14
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		721		$ 814	$ 735		$ 871
Total Gains (Losses) Included in Net Income		(1)		(1)	(1)		(1)
Total gains (losses) included in other comprehensive income (loss)		14		14	8		28
Purchases		0		14	6		14
Settlements		(3)		(51)	(17)		(122)
Balance, at the end of the period		731		790	731		790
Changes in unrealized gains (losses) in net income relating to assets held at the end of the period		(1)			(1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI					8
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		17		18	17		64
Total gains (losses) included in other comprehensive income (loss)		1			1
Purchases		38		27	38		27
Settlements							(1)
Transfers out of Level 3				1			(46)
Balance, at the end of the period		56		44	56		44
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI					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		300		379	389		374
Total gains (losses) included in other comprehensive income (loss)		52		5	(37)		10
Balance, at the end of the period		352		384	352		384
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI					(37)
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		1,038		1,211	1,141		1,309
Total Gains (Losses) Included in Net Income	[1]	(1)		(1)	(1)		(1)
Total gains (losses) included in other comprehensive income (loss)		67		19	(28)		38
Purchases		38		41	44		41
Settlements		(3)		(51)	(17)		(123)
Transfers out of Level 3				1			(46)
Balance, at the end of the period		1,139		1,218	1,139		1,218
Changes in unrealized gains (losses) in net income relating to assets held at the end of the period		$ (1)	[1]	$ 0	(1)	[1]	$ 0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI					$ (28)

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