Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 1,752		$ 1,752			$ 1,344
Accumulated other comprehensive income, net of tax, end of period	1,752		1,752
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	2,673	$ 2,357	2,094	$ 2,719
Other comprehensive income before reclassification, before tax	119	(363)	801	(620)
Reclassification adjustment, before tax	(57)	(2)	(160)	(107)
Effect on other comprehensive income, before tax	62	(365)	641	(727)
Accumulated other comprehensive income, before tax, end of period	2,735	1,992	2,735	1,992
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	925	815	722	942
Other comprehensive income before reclassification, tax	41	(126)	280	(216)
Reclassification adjustment, tax	(20)	(1)	(56)	(38)
Effect on other comprehensive income, tax	21	(127)	224	(254)
Accumulated other comprehensive income, tax, end of period	946	688	946	688
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,789	1,304	1,789	1,304	$ 1,748	1,372	$ 1,542	$ 1,777
Other comprehensive income before reclassification, net of tax	78	(237)	521	(404)
Reclassification adjustment, net of tax	(37)	(1)	(104)	(69)
Effect on other comprehensive income, net of tax	41	(238)	417	(473)
Accumulated other comprehensive income, net of tax, end of period	1,789	1,304	1,789	1,304
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(40)	(33)	(42)	(36)
Other comprehensive income before reclassification, before tax	0	0	0	0
Reclassification adjustment, before tax	0	1	2	4
Effect on other comprehensive income, before tax	0	1	2	4
Accumulated other comprehensive income, before tax, end of period	(40)	(32)	(40)	(32)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(13)	(11)	(14)	(12)
Other comprehensive income before reclassification, tax	0	0	0	0
Reclassification adjustment, tax	0	0	1	1
Effect on other comprehensive income, tax	0	0	1	1
Accumulated other comprehensive income, tax, end of period	(13)	(11)	(13)	(11)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(27)	(21)	(27)	(21)	(27)	(28)	(22)	(24)
Other comprehensive income before reclassification, net of tax	0	0	0	0
Reclassification adjustment, net of tax	0	1	1	3
Effect on other comprehensive income, net of tax	0	1	1	3
Accumulated other comprehensive income, net of tax, end of period	(27)	(21)	(27)	(21)
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)	(8)	1	(12)
Other comprehensive income before reclassification, before tax	(4)	5	(13)	11
Reclassification adjustment, before tax	1	(1)	(1)	(3)
Effect on other comprehensive income, before tax	(3)	4	(14)	8
Accumulated other comprehensive income, before tax, end of period	(13)	(4)	(13)	(4)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(3)	(2)	1	(3)
Other comprehensive income before reclassification, tax	(1)	1	(4)	3
Reclassification adjustment, tax	1	0	0	(1)
Effect on other comprehensive income, tax	0	1	(4)	2
Accumulated other comprehensive income, tax, end of period	(3)	(1)	(3)	(1)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(10)	(3)	(10)	(3)	(7)	0	(6)	(9)
Other comprehensive income before reclassification, net of tax	(3)	4	(9)	8
Reclassification adjustment, net of tax	0	(1)	(1)	(2)
Effect on other comprehensive income, net of tax	(3)	3	(10)	6
Accumulated other comprehensive income, net of tax, end of period	(10)	(3)	(10)	(3)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	2,623	2,316	2,053	2,671
Change in unrealized gains, net, on investments available for sale, before tax	62	(365)	641	(727)
Change in pension obligations, before tax	0	1	2	4
Change in life deferred acquisition costs, life policy reserves and other, before tax	(3)	4	(14)	8
Effect on other comprehensive income, before tax	59	(360)	629	(715)
Accumulated other comprehensive income, before tax, end of period	2,682	1,956	2,682	1,956
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	909	802	709	927
Change in unrealized gains, net, on investments available for sale, tax	21	(127)	224	(254)
Change in pension obligations, tax	0	0	1	1
Change in life deferred acquisition costs, life policy reserves and other, tax	0	1	(4)	2
Effect on other comprehensive income, tax	21	(126)	221	(251)
Accumulated other comprehensive income, tax, end of period	930	676	930	676
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,752	1,280	1,752	1,280	$ 1,714	$ 1,344	$ 1,514	$ 1,744
Change in unrealized gains, net, on investments available for sale, net of tax	41	(238)	417	(473)
Change in pension obligations, net of tax	0	1	1	3
Change in life deferred acquisition costs, life policy reserves and other, net of tax	(3)	3	(10)	6
Effect on other comprehensive income, net of tax	38	(234)	408	(464)
Accumulated other comprehensive income, net of tax, end of period	$ 1,752	$ 1,280	$ 1,752	$ 1,280