Fair Value, Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fixed Maturities Available-for-sale [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	$ 633	$ 419
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	2	0
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	60	41
Purchases	463	304
Sales	(12)	0
Settlements	(45)	(27)
Transfers into Level 3	40	45
Transfers out of Level 3	(17)	(149)
Ending balance	1,124	633
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	0	0
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	62	35
Corporate Bonds and Other [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	468	222
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	1
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	43	33
Purchases	264	256
Sales	(3)
Settlements	(13)	(11)
Transfers into Level 3	10
Transfers out of Level 3		(32)
Ending balance	770	468
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	43	28
States, Municipalities and Political Subdivisions [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	1
Purchases	45
Ending balance	46
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	1
Asset-Backed [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	165	197
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	1
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	16	8
Purchases	154	48
Sales	(9)
Settlements	(32)	(16)
Transfers into Level 3	30	45
Transfers out of Level 3	(17)	(117)
Ending balance	308	165
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	18	7
Fixed Maturities Trading [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	4	6
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	4	(2)
Ending balance	8	4
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	4	(2)
Total Fixed Maturities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	637	425
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	6	(2)
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	60	41
Purchases	463	304
Sales	(12)	0
Settlements	(45)	(27)
Transfers into Level 3	40	45
Transfers out of Level 3	(17)	(149)
Ending balance	1,132	637
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	4	(2)
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	62	35
Equity Securities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	19	19
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(6)	(2)
Purchases	15	2
Transfers into Level 3	15
Ending balance	43	19
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	$ (6)	$ (2)