Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 204		$ 448
Accumulated other comprehensive income, net of tax, end of period	204
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Other comprehensive income before reclassification, before tax	(399)	$ 244
Reclassification adjustment, before tax	75	(2)
Effect on other comprehensive income, before tax	(324)	242
Accumulated other comprehensive income, before tax, end of period	266	288
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income before reclassification, tax	(84)	51
Reclassification adjustment, tax	16	(1)
Effect on other comprehensive income, tax	(68)	50
Accumulated other comprehensive income, tax, end of period	55	59
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	211	229
Other comprehensive income before reclassification, net of tax	(315)	193
Reclassification adjustment, net of tax	59	(1)
Effect on other comprehensive income, net of tax	(256)	192
Accumulated other comprehensive income, net of tax, end of period	211	229
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(9)	(16)
Other comprehensive income before reclassification, before tax	0	0
Reclassification adjustment, before tax	1	0
Effect on other comprehensive income, before tax	1	0
Accumulated other comprehensive income, before tax, end of period	(8)	(16)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	0	(2)
Other comprehensive income before reclassification, tax	0	0
Reclassification adjustment, tax	0	0
Effect on other comprehensive income, tax	0	0
Accumulated other comprehensive income, tax, end of period	0	(2)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(8)	(14)	(9)	$ (14)
Other comprehensive income before reclassification, net of tax	0	0
Reclassification adjustment, net of tax	1	0
Effect on other comprehensive income, net of tax	1	0
Accumulated other comprehensive income, net of tax, end of period	(8)	(14)
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	(13)	(1)
Other comprehensive income before reclassification, before tax	14	0
Reclassification adjustment, before tax	0	(5)
Effect on other comprehensive income, before tax	14	(5)
Accumulated other comprehensive income, before tax, end of period	1	(6)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(3)	0
Other comprehensive income before reclassification, tax	3	0
Reclassification adjustment, tax	0	(1)
Effect on other comprehensive income, tax	3	(1)
Accumulated other comprehensive income, tax, end of period	0	(1)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1	(5)	(10)	(1)
Other comprehensive income before reclassification, net of tax	11	0
Reclassification adjustment, net of tax	0	(4)
Effect on other comprehensive income, net of tax	11	(4)
Accumulated other comprehensive income, net of tax, end of period	1	(5)
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	(324)	242
Change in pension obligations, before tax	1	0
Change in life deferred acquisition costs, life policy reserves and other, before tax	14	(5)
Effect on other comprehensive income, before tax	(309)	237
Accumulated other comprehensive income, before tax, end of period	259	266
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Change in unrealized gains, net, on investments available for sale, tax	(68)	50
Change in pension obligations, tax	0	0
Change in life deferred acquisition costs, life policy reserves and other, tax	3	(1)
Effect on other comprehensive income, tax	(65)	49
Accumulated other comprehensive income, tax, end of period	55	56
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	204	210
Change in unrealized gains, net, on investments available for sale, net of tax	(256)	192
Change in pension obligations, net of tax	1	0
Change in life deferred acquisition costs, life policy reserves and other, net of tax	11	(4)
Effect on other comprehensive income, net of tax	(244)	188
Accumulated other comprehensive income, net of tax, end of period	204	210
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	590	46
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	123	9
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period			467	37
Previously Reported | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	568	29
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	$ 120	$ 7
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period			$ 448	$ 22