Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 1,716		$ 1,744
Accumulated other comprehensive income, net of tax, end of period	1,716		1,744
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	2,719	2,335
Other comprehensive income before reclassification, before tax	3	135
Reclassification adjustment, before tax	(46)	(18)
Effect on other comprehensive income, before tax	(43)	117
Accumulated other comprehensive income, before tax, end of period	2,676	2,452
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	942	808
Other comprehensive income before reclassification, tax	1	48
Reclassification adjustment, tax	(16)	(7)
Effect on other comprehensive income, tax	(15)	41
Accumulated other comprehensive income, tax, end of period	927	849
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,749	1,603	1,777	1,527
Other comprehensive income before reclassification, net of tax	2	87
Reclassification adjustment, net of tax	(30)	(11)
Effect on other comprehensive income, net of tax	(28)	76
Accumulated other comprehensive income, net of tax, end of period	1,749	1,603	1,777	1,527
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	(36)	(18)
Other comprehensive income before reclassification, before tax	0	(2)
Reclassification adjustment, before tax	1	1
Effect on other comprehensive income, before tax	1	(1)
Accumulated other comprehensive income, before tax, end of period	(35)	(19)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(12)	(6)
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	(12)	(6)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(23)	(13)	(24)	(12)
Other comprehensive income before reclassification, net of tax	0	(2)
Reclassification adjustment, net of tax	1	1
Effect on other comprehensive income, net of tax	1	(1)
Accumulated other comprehensive income, net of tax, end of period	(23)	(13)	(24)	(12)
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	(12)	(16)
Other comprehensive income before reclassification, before tax	(1)	3
Reclassification adjustment, before tax	(1)	(4)
Effect on other comprehensive income, before tax	(2)	(1)
Accumulated other comprehensive income, before tax, end of period	(14)	(17)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	(3)	(5)
Other comprehensive income before reclassification, tax	(1)	1
Reclassification adjustment, tax	0	(1)
Effect on other comprehensive income, tax	(1)	0
Accumulated other comprehensive income, tax, end of period	(4)	(5)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	(10)	(12)	(9)	(11)
Other comprehensive income before reclassification, net of tax	0	2
Reclassification adjustment, net of tax	(1)	(3)
Effect on other comprehensive income, net of tax	(1)	(1)
Accumulated other comprehensive income, net of tax, end of period	(10)	(12)	(9)	(11)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before tax, beginning of period	2,671	2,301
Change in unrealized gains, net, on investments available for sale, before tax	(43)	117
Change in pension obligations, before tax	1	(1)
Change in life deferred acquisition costs, life policy reserves and other, before tax	(2)	(1)
Effect on other comprehensive income, before tax	(44)	115
Accumulated other comprehensive income, before tax, end of period	2,627	2,416
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	927	797
Change in unrealized gains, net, on investments available for sale, tax	(15)	41
Change in pension obligations, tax	0	0
Change in life deferred acquisition costs, life policy reserves and other, tax	(1)	0
Effect on other comprehensive income, tax	(16)	41
Accumulated other comprehensive income, tax, end of period	911	838
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,716	1,578	1,744	1,504
Change in unrealized gains, net, on investments available for sale, net of tax	(28)	76
Change in pension obligations, net of tax	1	(1)
Change in life deferred acquisition costs, life policy reserves and other, net of tax	(1)	(1)
Effect on other comprehensive income, net of tax	(28)	74
Accumulated other comprehensive income, net of tax, end of period	$ 1,716	$ 1,578	$ 1,744	$ 1,504