Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pre-tax
Unrealized net holding gains arising during the period, net of related offsets, Pre-tax	$ 211	$ 866
Less: reclassification adjustment of realized capital gains and losses, Pre-tax	102	140
Unrealized net capital gains and losses, Pre-tax	109	726
Unrecognized pension and other postretirement benefit cost arising during the period, Pre-tax	2	(12)
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses, Pre-tax	(66)	(43)
Unrecognized pension and other postretirement benefit cost, Pre-tax	68	31
Unrealized foreign currency translation adjustments, Pre-tax	(18)	14
Other comprehensive income (loss), Pre-tax	159	771
Tax
Unrealized net holding gains arising during the period, net of related offsets, Tax	(74)	(301)
Less: reclassification adjustment of realized capital gains and losses, Tax	(36)	(49)
Unrealized net capital gains and losses, Tax	(38)	(252)
Unrecognized pension and other postretirement benefit cost arising during the period, Tax		4
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses, Tax	23	15
Unrecognized pension and other postretirement benefit cost, Tax	(23)	(11)
Unrealized foreign currency translation adjustments, Tax	6	(5)
Other comprehensive income (loss), Tax	(55)	(268)
After-tax
Unrealized net holding gains arising during the period, net of related offsets, After-tax	137	565
Less: reclassification adjustment of realized capital gains and losses, After-tax	66	91
Unrealized net capital gains and losses, After-tax	71	474
Unrecognized pension and other postretirement benefit cost arising during the period, After-tax	2	(8)
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses, After-tax	(43)	(28)
Unrecognized pension and other postretirement benefit cost, After-tax	45	20
Unrealized foreign currency translation adjustments, After-tax	(12)	9
Other comprehensive income, after-tax	104	503
Net income	709	766
Comprehensive income	$ 813	$ 1,269