Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 364		$ 364			$ 22
Accumulated other comprehensive income, net of tax, end of period	364		364
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	288	$ 164	46	$ 385
Cumulative effect of change in accounting for equity securities, before tax						0		$ (3,155)
Other comprehensive income before reclassification, before tax	199	(78)	443	(295)
Reclassification adjustment, before tax	1	(2)	(1)	(6)
Effect on other comprehensive income, before tax	200	(80)	442	(301)
Accumulated other comprehensive income, before tax, end of period	488	84	488	84
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	59	35	9	81
Cumulative effect of change in accounting for equity securities, tax						0		(652)
Other comprehensive income before reclassification, tax	43	(18)	93	(63)
Reclassification adjustment, tax	0	0	0	(1)
Effect on other comprehensive income, tax	43	(18)	93	(64)
Accumulated other comprehensive income, tax, end of period	102	17	102	17
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	386	67	386	67	$ 229	37	$ 129	304
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax						0		(2,503)
Other comprehensive income before reclassification, net of tax	156	(60)	350	(232)
Reclassification adjustment, net of tax	1	(2)	(1)	(5)
Effect on other comprehensive income, net of tax	157	(62)	349	(237)
Accumulated other comprehensive income, net of tax, end of period	386	67	386	67
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(16)	(12)	(16)	(12)
Other comprehensive income before reclassification, before tax	0	0	0	0
Reclassification adjustment, before tax	1	1	1	1
Effect on other comprehensive income, before tax	1	1	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)	(14)	(14)	(11)	(11)
Other comprehensive income before reclassification, net of tax	0	0	0	0
Reclassification adjustment, net of tax	1	1	1	1
Effect on other comprehensive income, net of tax	1	1	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	(6)	(4)	(1)	(10)
Other comprehensive income before reclassification, before tax	(6)	0	(6)	6
Reclassification adjustment, before tax	1	2	(4)	2
Effect on other comprehensive income, before tax	(5)	2	(10)	8
Accumulated other comprehensive income, before tax, end of period	(11)	(2)	(11)	(2)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(1)	(1)	0	(2)
Other comprehensive income before reclassification, tax	(1)	0	(1)	1
Reclassification adjustment, tax	0	1	(1)	1
Effect on other comprehensive income, tax	(1)	1	(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	(9)	(2)	(9)	(2)	(5)	(1)	(3)	(8)
Other comprehensive income before reclassification, net of tax	(5)	0	(5)	5
Reclassification adjustment, net of tax	1	1	(3)	1
Effect on other comprehensive income, net of tax	(4)	1	(8)	6
Accumulated other comprehensive income, net of tax, end of period	(9)	(2)	(9)	(2)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	266	148	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	200	(80)	442	(301)
Change in pension obligations, before tax	1	1	1	1
Change in life deferred acquisition costs, life policy reserves and other, before tax	(5)	2	(10)	8
Effect on other comprehensive income, before tax	196	(77)	433	(292)
Accumulated other comprehensive income, before tax, end of period	462	71	462	71
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	56	33	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	43	(18)	93	(64)
Change in pension obligations, tax	0	0	0	0
Change in life deferred acquisition costs, life policy reserves and other, tax	(1)	1	(2)	2
Effect on other comprehensive income, tax	42	(17)	91	(62)
Accumulated other comprehensive income, tax, end of period	98	16	98	16
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	364	55	364	55	210	22	115	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	157	(62)	349	(237)
Change in pension obligations, net of tax	1	1	1	1
Change in life deferred acquisition costs, life policy reserves and other, net of tax	(4)	1	(8)	6
Effect on other comprehensive income, net of tax	154	(60)	342	(230)
Accumulated other comprehensive income, net of tax, end of period	$ 364	$ 55	364	55
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