Fair Value, Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fixed Maturities Available-for-Sale [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	$ 777	$ 531	$ 633	$ 419
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	0	0	0	0
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	14	15	45	42
Purchases	194	101	345	253
Sales	0	0	(9)	0
Settlements	(17)	(7)	(31)	(19)
Transfers into Level 3	8	0	8	45
Transfers out of Level 3	(2)	(16)	(17)	(116)
Ending balance	974	624	974	624
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	0	0	0	0
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	13	16	48	38
Corporate Bonds and Other [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	555	338	468	222
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	5	14	27	34
Purchases	129	79	200	211
Settlements	(3)	(3)	(9)	(7)
Transfers into Level 3	8		8
Transfers out of Level 3				(32)
Ending balance	694	428	694	428
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	5	14	29	29
States, Municipalities and Political Subdivisions [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	0		0
Purchases	45		45
Ending balance	45		45
Asset-Backed [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	222	193	165	197
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	9	1	18	8
Purchases	20	22	100	42
Sales			(9)
Settlements	(14)	(4)	(22)	(12)
Transfers into Level 3				45
Transfers out of Level 3	(2)	(16)	(17)	(84)
Ending balance	235	196	235	196
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	8	2	19	9
Fixed Maturities Trading [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	4	4	4	6
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	4		4	(2)
Ending balance	8	4	8	4
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	4		4	(2)
Total Fixed Maturities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	781	535	637	425
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	4	0	4	(2)
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	14	15	45	42
Purchases	194	101	345	253
Sales	0	0	(9)	0
Settlements	(17)	(7)	(31)	(19)
Transfers into Level 3	8	0	8	45
Transfers out of Level 3	(2)	(16)	(17)	(116)
Ending balance	982	628	982	628
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	4	0	4	(2)
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	13	16	48	38
Equity Securities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	27	23	19	19
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income			(7)	2
Purchases	12		12	2
Transfers into Level 3			15
Ending balance	$ 39	$ 23	39	23
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities			$ (7)	$ 2