Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pre-tax
Unrealized net holding gains arising during the period, net of related offsets, Pre-tax	$ 2,428	$ 1,493	$ 2,717
Less: reclassification adjustment of realized capital gains and losses, Pre-tax	225	795	(221)
Unrealized net capital gains and losses, Pre-tax	2,203	698	2,938
Unrealized foreign currency translation adjustments, Pre-tax	22	(18)	35
Unrecognized pension and other postretirement benefit cost, Pre-tax	(468)	(371)	142
Other comprehensive income (loss), Pre-tax	1,757	309	3,115
Tax
Unrealized net holding gains arising during the period, net of related offsets, Tax	(848)	(524)	(950)
Less: reclassification adjustment of realized capital gains and losses, Tax	(79)	(278)	77
Unrealized net capital gains and losses, Tax	(769)	(246)	(1,027)
Unrealized foreign currency translation adjustments, Tax	(8)	6	(12)
Unrecognized pension and other postretirement benefit cost, Tax	166	132	(48)
Other comprehensive income (loss), Tax	(611)	(108)	(1,087)
After-tax
Unrealized net holding gains arising during the period, net of related offsets, After-tax	1,580	969	1,767
Less: reclassification adjustment of realized capital gains and losses, After-tax	146	517	(144)
Unrealized net capital gains and losses, After-tax	1,434	452	1,911
Unrealized foreign currency translation adjustments, After-tax	14	(12)	23
Unrecognized pension and other postretirement benefit cost, After-tax	(302)	(239)	94
Other comprehensive income, after-tax	$ 1,146	$ 201	$ 2,028