Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	$ 1,267		$ 1,267			$ 1,129
Accumulated other comprehensive income, net of tax, end of period	1,267		1,267			1,129
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated unrealized gains, net, on investments available for sale, before tax, beginning of period	1,987	1,664	1,875	1,489
Other comprehensive income before reclassification, before tax	82	262	246	456
Reclassification adjustment for realized gains, net, included in net income, before tax	(20)	(9)	(72)	(28)
Effect on other comprehensive income, before tax	62	253	174	428
Accumulated unrealized gains, net, on investments available for sale, before tax, end of period	2,049	1,917	2,049	1,917
Accumulated Other Comprehensive Income Loss Tax [Abstract]
Accumulated unrealized gains, net, on investments available for sale and other invested assets, tax, beginning of period	708	662	708	662
Other comprehensive income before reclassification, tax	29	93	85	160
Reclassification adjustment for realized gains, net, included in net income, tax	(7)	(4)	(24)	(10)
Effect on other comprehensive income, tax	22	89	61	150
Accumulated unrealized gains, net, on investments available for sale and other invested assets, tax, end of period	686	573	647	512
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated unrealized gains, net, on investments available for sale and other invested assets, net of tax, beginning of period	1,301	1,091	1,228	977
Other comprehensive income before reclassification , net of tax	53	169	161	296
Reclassification adjustment for realized gains, net, included in net income, net of tax	(13)	(5)	(48)	(18)
Effect on other comprehensive income, net of tax	40	164	113	278
Accumulated unrealized gains, net, on investments available for sale and other invested assets, net of tax, end of period	1,341	1,255	1,341	1,255
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Other comprehensive income before reclassification, before tax	0	0
Accumulated unrealized losses, net, for pension obligations, before Tax, beginning of period	(96)	(85)	(101)	(88)
Reclassification adjustment for amortization of actuarial loss and prior service cost, net, included in net income, before tax	2	2
Effect on other comprehensive income, before tax	2	2	7	5
Accumulated unrealized losses, net, for pension obligations, before Tax, end of period	(94)	(83)	(94)	(83)
Accumulated Other Comprehensive Income Loss Tax [Abstract]
Other comprehensive income before reclassification, tax	0	0
Accumulated unrealized losses, net, for pension obligations, tax, beginning of period	(33)	(30)	(35)	(31)
Reclassification adjustment for amortization of actuarial loss and prior service cost, net, included in net income, tax	1	1
Effect on other comprehensive income, tax	1	1	3	2
Accumulated unrealized losses, net, for pension obligations, tax, end of period	(32)	(29)	(32)	(29)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other comprehensive income before reclassification , net of tax	0	0
Accumulated unrealized losses, net, for pension obligations, net of tax, beginning of period	(63)	(55)	(66)	(57)
Reclassification adjustment for amortization of actuarial loss and prior service cost,net, included in net income, net of tax	1	1
Effect on other comprehensive income, net of tax	1	1	4	3
Accumulated unrealized losses, net, for pension obligations, net of tax, end of period	(62)	(54)	(62)	(54)
Accumulated Net Unrealized Gain (Loss) on Deferred Costs, Reserves And Other
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Other comprehensive income before reclassification, before tax	9	(5)	36	(15)
Other Comprehensive Income (Loss), Reclassification Adjustment for Life Deferred Acquisition Costs, Life Policy Reserves and Other, Before Tax	(2)	(1)	(5)	(1)
Accumulated unrealized losses, net, on life deferred acquisition costs, life policy reserves and other, before tax, beginning of period	(26)	(39)	(50)	(29)
Effect on other comprehensive income, before tax	7	(6)	31	(16)
Accumulated unrealized losses, net, on life deferred acquisition costs, life policy reserves and other, before tax, end of period	(19)	(45)	(19)	(45)
Accumulated Other Comprehensive Income Loss Tax [Abstract]
Other comprehensive income before reclassification, tax	2	(2)	12	(5)
Accumulated unrealized losses, net, on life deferred acquisition costs, life policy reserves and other, tax, beginning of period	(9)	(13)	(17)	(10)
Other Comprehensive Income (Loss), Reclassification Adjustment for Life Deferred Acquisition Costs, Life Policy Reserves and Other, Tax	0	0	(2)	0
Effect on other comprehensive income, tax	2	(2)	10	(5)
Accumulated unrealized losses, net, on life deferred acquisition costs, life policy reserves and other, tax, end of period	(7)	(15)	(7)	(15)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other comprehensive income before reclassification , net of tax	7	(3)	24	(10)
Accumulated unrealized losses, net, on life deferred acquisition costs, life policy reserves and other, beginning of period, net of tax	(17)	(26)	(33)	(19)
Other Comprehensive Income (Loss), Reclassification Adjustment for Life Deferred Acquisition Costs, Life Policy Reserves and Other, Net of Tax	(2)	(1)	(3)	(1)
Effect on other comprehensive income, net of tax	5	(4)	21	(11)
Accumulated unrealized losses, net, on life deferred acquisition costs, life policy reserves and other, end of period, net of tax	(12)	(30)	(12)	(30)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss Before Tax [Abstract]
Accumulated other comprehensive income, before taxes, beginning of period	1,865	1,540	1,724	1,372
Change in unrealized gains, net, on investments available for sale, before Tax	62	253	174	428
Change in pension obligations, before tax	2	2	7	5
Change in life deferred acquisition costs, life policy reserves and other, before Tax	7	(6)	31	(16)
Effect on other comprehensive income, before Tax	71	249	212	417
Accumulated other comprehensive income, before taxes, end of period	1,936	1,789	1,936	1,789
Accumulated Other Comprehensive Income Loss Tax [Abstract]
Accumulated other comprehensive income, tax, beginning of period	644	530	595	471
Change in unrealized gains, net, on investments available for sale and other invested assets, tax	22	89	61	150
Change in pension obligations, tax	1	1	3	2
Change in life deferred acquisition costs, life policy reserves and other, tax	2	(2)	10	(5)
Effect on other comprehensive income, tax	25	88	74	147
Accumulated other comprehensive income, tax, end of period	669	618	669	618
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated other comprehensive income, net of tax, beginning of period	1,267	1,171	1,267	1,171	1,221	1,129	1,010	901
Change in unrealized gains, net, on investments available for sale, net of tax	40	164	113	278
Change in pension obligations, net of tax	1	1	4	3
Change in life deferred acquisition costs, life policy reserves and other, net of tax	5	(4)	21	(11)
Effect on other comprehensive income, net of tax	46	161	138	270
Accumulated other comprehensive income, net of tax, end of period	$ 1,267	$ 1,171	$ 1,267	$ 1,171	$ 1,221	$ 1,129	$ 1,010	$ 901