Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 1,514		$ 1,514			$ 1,744
Accumulated other comprehensive income, net of tax, end of period	1,514		1,514
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	2,676	$ 2,452	2,719	$ 2,335
Other comprehensive income before reclassification, before tax	(260)	252	(257)	387
Reclassification adjustment, before tax	(59)	(17)	(105)	(35)
Effect on other comprehensive income, before tax	(319)	235	(362)	352
Accumulated other comprehensive income, before tax, end of period	2,357	2,687	2,357	2,687
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	927	849	942	808
Other comprehensive income before reclassification, tax	(91)	87	(90)	135
Reclassification adjustment, tax	(21)	(5)	(37)	(12)
Effect on other comprehensive income, tax	(112)	82	(127)	123
Accumulated other comprehensive income, tax, end of period	815	931	815	931
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,542	1,756	1,542	1,756	$ 1,749	1,777	$ 1,603	$ 1,527
Other comprehensive income before reclassification, net of tax	(169)	165	(167)	252
Reclassification adjustment, net of tax	(38)	(12)	(68)	(23)
Effect on other comprehensive income, net of tax	(207)	153	(235)	229
Accumulated other comprehensive income, net of tax, end of period	1,542	1,756	1,542	1,756
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(35)	(19)	(36)	(18)
Other comprehensive income before reclassification, before tax	0	0	0	0
Reclassification adjustment, before tax	2	0	3	(1)
Effect on other comprehensive income, before tax	2	0	3	(1)
Accumulated other comprehensive income, before tax, end of period	(33)	(19)	(33)	(19)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(12)	(6)	(12)	(6)
Other comprehensive income before reclassification, tax	0	0	0	0
Reclassification adjustment, tax	1	0	1	0
Effect on other comprehensive income, tax	1	0	1	0
Accumulated other comprehensive income, tax, end of period	(11)	(6)	(11)	(6)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(22)	(13)	(22)	(13)	(23)	(24)	(13)	(12)
Other comprehensive income before reclassification, net of tax	0	0	0	0
Reclassification adjustment, net of tax	1	0	2	(1)
Effect on other comprehensive income, net of tax	1	0	2	(1)
Accumulated other comprehensive income, net of tax, end of period	(22)	(13)	(22)	(13)
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	(14)	(17)	(12)	(16)
Other comprehensive income before reclassification, before tax	7	(2)	6	1
Reclassification adjustment, before tax	(1)	3	(2)	(1)
Effect on other comprehensive income, before tax	6	1	4	0
Accumulated other comprehensive income, before tax, end of period	(8)	(16)	(8)	(16)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(4)	(5)	(3)	(5)
Other comprehensive income before reclassification, tax	3	0	2	1
Reclassification adjustment, tax	(1)	0	(1)	(1)
Effect on other comprehensive income, tax	2	0	1	0
Accumulated other comprehensive income, tax, end of period	(2)	(5)	(2)	(5)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(6)	(11)	(6)	(11)	(10)	(9)	(12)	(11)
Other comprehensive income before reclassification, net of tax	4	(2)	4	0
Reclassification adjustment, net of tax	0	3	(1)	0
Effect on other comprehensive income, net of tax	4	1	3	0
Accumulated other comprehensive income, net of tax, end of period	(6)	(11)	(6)	(11)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	2,627	2,416	2,671	2,301
Change in unrealized gains, net, on investments available for sale, before tax	(319)	235	(362)	352
Change in pension obligations, before tax	2	0	3	(1)
Change in life deferred acquisition costs, life policy reserves and other, before tax	6	1	4	0
Effect on other comprehensive income, before tax	(311)	236	(355)	351
Accumulated other comprehensive income, before tax, end of period	2,316	2,652	2,316	2,652
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	911	838	927	797
Change in unrealized gains, net, on investments available for sale, tax	(112)	82	(127)	123
Change in pension obligations, tax	1	0	1	0
Change in life deferred acquisition costs, life policy reserves and other, tax	2	0	1	0
Effect on other comprehensive income, tax	(109)	82	(125)	123
Accumulated other comprehensive income, tax, end of period	802	920	802	920
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,514	1,732	1,514	1,732	$ 1,716	$ 1,744	$ 1,578	$ 1,504
Change in unrealized gains, net, on investments available for sale, net of tax	(207)	153	(235)	229
Change in pension obligations, net of tax	1	0	2	(1)
Change in life deferred acquisition costs, life policy reserves and other, net of tax	4	1	3	0
Effect on other comprehensive income, net of tax	(202)	154	(230)	228
Accumulated other comprehensive income, net of tax, end of period	$ 1,514	$ 1,732	$ 1,514	$ 1,732