Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 625		$ 769
Accumulated other comprehensive income, net of tax, end of period	625
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Other comprehensive income before reclassification, before tax	(193)	$ (399)
Reclassification adjustment, before tax	(3)	75
Effect on other comprehensive income, before tax	(196)	(324)
Accumulated other comprehensive income, before tax, end of period	830	266
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income before reclassification, tax	(41)	(84)
Reclassification adjustment, tax	0	16
Effect on other comprehensive income, tax	(41)	(68)
Accumulated other comprehensive income, tax, end of period	174	55
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	656	211
Other comprehensive income before reclassification, net of tax	(152)	(315)
Reclassification adjustment, net of tax	(3)	59
Effect on other comprehensive income, net of tax	(155)	(256)
Accumulated other comprehensive income, net of tax, end of period	656	211
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(41)	(9)
Other comprehensive income before reclassification, before tax	2	0
Reclassification adjustment, before tax	2	1
Effect on other comprehensive income, before tax	4	1
Accumulated other comprehensive income, before tax, end of period	(37)	(8)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(7)	0
Other comprehensive income before reclassification, tax	1	0
Reclassification adjustment, tax	0	0
Effect on other comprehensive income, tax	1	0
Accumulated other comprehensive income, tax, end of period	(6)	0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(31)	(8)	(34)	$ (9)
Other comprehensive income before reclassification, net of tax	1	0
Reclassification adjustment, net of tax	2	1
Effect on other comprehensive income, net of tax	3	1
Accumulated other comprehensive income, net of tax, end of period	(31)	(8)
Accumulated Net Unrealized Gain (Loss) on Deferred Costs, Reserves And Other
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(10)	(13)
Other comprehensive income before reclassification, before tax	10	14
Reclassification adjustment, before tax	0	0
Effect on other comprehensive income, before tax	10	14
Accumulated other comprehensive income, before tax, end of period	0	1
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(2)	(3)
Other comprehensive income before reclassification, tax	2	3
Reclassification adjustment, tax	0	0
Effect on other comprehensive income, tax	2	3
Accumulated other comprehensive income, tax, end of period	0	0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	0	1	(8)	(10)
Other comprehensive income before reclassification, net of tax	8	11
Reclassification adjustment, net of tax	0	0
Effect on other comprehensive income, net of tax	8	11
Accumulated other comprehensive income, net of tax, end of period	0	1
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Change in unrealized gains, net, on investments available for sale, before tax	(196)	(324)
Change in pension obligations, before tax	4	1
Change in life deferred acquisition costs, life policy reserves and other, before tax	10	14
Effect on other comprehensive income, before tax	(182)	(309)
Accumulated other comprehensive income, before tax, end of period	793	259
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Change in unrealized gains, net, on investments available for sale, tax	(41)	(68)
Change in pension obligations, tax	1	0
Change in life deferred acquisition costs, life policy reserves and other, tax	2	3
Effect on other comprehensive income, tax	(38)	(65)
Accumulated other comprehensive income, tax, end of period	168	55
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	625	204
Change in unrealized gains, net, on investments available for sale, net of tax	(155)	(256)
Change in pension obligations, net of tax	3	1
Change in life deferred acquisition costs, life policy reserves and other, net of tax	8	11
Effect on other comprehensive income, net of tax	(144)	(244)
Accumulated other comprehensive income, net of tax, end of period	625	204
Previously Reported | Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	1,026	590
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	215	123
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period			811	467
Previously Reported | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	975	568
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	$ 206	$ 120
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period			$ 769	$ 448