Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 442		$ 442			$ 22
Accumulated other comprehensive income, net of tax, end of period	442		442
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	488	$ 84	46	$ 385
Cumulative effect of change in accounting for equity securities, before tax						0		$ (3,155)
Other comprehensive income before reclassification, before tax	99	(76)	542	(371)
Reclassification adjustment, before tax	1	(1)	0	(7)
Effect on other comprehensive income, before tax	100	(77)	542	(378)
Accumulated other comprehensive income, before tax, end of period	588	7	588	7
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	102	17	9	81
Cumulative effect of change in accounting for equity securities, tax						0		(652)
Other comprehensive income before reclassification, tax	21	(17)	114	(80)
Reclassification adjustment, tax	0	0	0	(1)
Effect on other comprehensive income, tax	21	(17)	114	(81)
Accumulated other comprehensive income, tax, end of period	123	0	123	0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	465	7	465	7	$ 386	37	$ 67	304
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax						0		(2,503)
Other comprehensive income before reclassification, net of tax	78	(59)	428	(291)
Reclassification adjustment, net of tax	1	(1)	0	(6)
Effect on other comprehensive income, net of tax	79	(60)	428	(297)
Accumulated other comprehensive income, net of tax, end of period	465	7	465	7
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(15)	(11)	(16)	(12)
Other comprehensive income before reclassification, before tax	0	0	0	0
Reclassification adjustment, before tax	0	0	1	1
Effect on other comprehensive income, before tax	0	0	1	1
Accumulated other comprehensive income, before tax, end of period	(15)	(11)	(15)	(11)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(2)	(1)	(2)	(1)
Other comprehensive income before reclassification, tax	0	0	0	0
Reclassification adjustment, tax	0	0	0	0
Effect on other comprehensive income, tax	0	0	0	0
Accumulated other comprehensive income, tax, end of period	(2)	(1)	(2)	(1)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(13)	(10)	(13)	(10)	(13)	(14)	(10)	(11)
Other comprehensive income before reclassification, net of tax	0	0	0	0
Reclassification adjustment, net of tax	0	0	1	1
Effect on other comprehensive income, net of tax	0	0	1	1
Accumulated other comprehensive income, net of tax, end of period	(13)	(10)	(13)	(10)
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	(11)	(2)	(1)	(10)
Other comprehensive income before reclassification, before tax	(3)	0	(9)	6
Reclassification adjustment, before tax	2	1	(2)	3
Effect on other comprehensive income, before tax	(1)	1	(11)	9
Accumulated other comprehensive income, before tax, end of period	(12)	(1)	(12)	(1)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(2)	0	0	(2)
Other comprehensive income before reclassification, tax	0	0	(2)	1
Reclassification adjustment, tax	0	0	0	1
Effect on other comprehensive income, tax	0	0	(2)	2
Accumulated other comprehensive income, tax, end of period	(2)	0	(2)	0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(10)	(1)	(10)	(1)	(9)	(1)	(2)	(8)
Other comprehensive income before reclassification, net of tax	(3)	0	(7)	5
Reclassification adjustment, net of tax	2	1	(2)	2
Effect on other comprehensive income, net of tax	(1)	1	(9)	7
Accumulated other comprehensive income, net of tax, end of period	(10)	(1)	(10)	(1)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	462	71	29	363
Cumulative effect of change in accounting for equity securities, before tax						0		(3,155)
Change in unrealized gains, net, on investments available for sale, before tax	100	(77)	542	(378)
Change in pension obligations, before tax	0	0	1	1
Change in life deferred acquisition costs, life policy reserves and other, before tax	(1)	1	(11)	9
Effect on other comprehensive income, before tax	99	(76)	532	(368)
Accumulated other comprehensive income, before tax, end of period	561	(5)	561	(5)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	98	16	7	78
Cumulative effect of change in accounting for equity securities, tax						0		(652)
Change in unrealized gains, net, on investments available for sale, tax	21	(17)	114	(81)
Change in pension obligations, tax	0	0	0	0
Change in life deferred acquisition costs, life policy reserves and other, tax	0	0	(2)	2
Effect on other comprehensive income, tax	21	(17)	112	(79)
Accumulated other comprehensive income, tax, end of period	119	(1)	119	(1)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	442	(4)	442	(4)	364	22	55	285
Cumulative effect of change in accounting for equity securities, net								(2,503)
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax					$ 0	0	$ 0	(2,503)
Change in unrealized gains, net, on investments available for sale, net of tax	79	(60)	428	(297)
Change in pension obligations, net of tax	0	0	1	1
Change in life deferred acquisition costs, life policy reserves and other, net of tax	(1)	1	(9)	7
Effect on other comprehensive income, net of tax	78	(59)	420	(289)
Accumulated other comprehensive income, net of tax, end of period	$ 442	$ (4)	442	(4)
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			46	3,540
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period			9	733
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period						37		2,807
Previously Reported | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period			29	3,518
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period			$ 7	$ 730
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period						$ 22		$ 2,788