Federal and Foreign Income Tax (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of effective income tax rate and statutory federal corporate tax rate [Abstract]
Income before federal and foreign income tax									$ 2,199	$ 2,988	$ 2,962
Tax at statutory federal income tax rate									770	1,046	1,037
Tax at statutory federal income tax rate, percentage of pre-tax income									35.00%	35.00%	35.00%
Tax exempt interest income									(243)	(241)	(239)
Tax exempt interest income, percentage of pre-tax income									(11.00%)	(8.10%)	(8.10%)
Other, net									(6)	9	(19)
Other, net, percentage of pre-tax income									(0.30%)	0.30%	(0.60%)
Federal and Foreign Income Tax	$ 150	$ 68	$ 127	$ 176	$ 234	$ 212	$ 184	$ 184	$ 521	$ 814	$ 779
Actual tax, percentage of pre-tax income									23.70%	27.20%	26.30%