Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pre- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	$ 486	$ 730
Less: reclassification adjustment of realized capital gains and losses	162	46
Unrealized net capital gains and losses	324	684
Unrealized foreign currency translation adjustments	(42)	(25)
Unrecognized pension and other postretirement benefit cost arising during the period	11	4
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses	(32)	(13)
Unrecognized pension and other postretirement benefit cost	43	17
Other comprehensive income	325	676
Tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(170)	(255)
Less: reclassification adjustment of realized capital gains and losses	(57)	(16)
Unrealized net capital gains and losses	(113)	(239)
Unrealized foreign currency translation adjustments	15	9
Unrecognized pension and other postretirement benefit cost arising during the period	(3)	(1)
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses	11	5
Unrecognized pension and other postretirement benefit cost	(14)	(6)
Other comprehensive income (loss), Tax	(112)	(236)
After- tax
Unrealized net holding gains and losses arising during the period, net of related offsets	316	475
Less: reclassification adjustment of realized capital gains and losses	105	30
Unrealized net capital gains and losses	211	445
Unrealized foreign currency translation adjustments	(27)	(16)
Unrecognized pension and other postretirement benefit cost arising during the period	8	3
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses	(21)	(8)
Unrecognized pension and other postretirement benefit cost	29	11
Other comprehensive income, after-tax	$ 213	$ 440