Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Federal
Current	$ 551	$ 51	$ 955	$ 457
Deferred	(92)	317	(24)	273
Federal income tax	459	368	931	730
State
Current	112	62	162	72
Deferred	(7)	28	(2)	22
State income tax	105	90	160	94
Total income tax provision	564	458	1,091	824
Reconciliation of expected income tax expense at the federal statutory rate of 35 percent to the Company's applicable income tax expense
Tax at statutory rate	680	573	1,321	1,061
State income tax, at statutory rates, net of federal tax benefit	68	58	104	61
Tax effect of
Tax credits, net of related expenses	(113)	(108)	(202)	(195)
Tax-exempt income	(55)	(57)	(110)	(113)
Noncontrolling interests	13	8	24	14
Other items	(29)	(16)	(46)	(4)
Applicable income taxes	$ 564	$ 458	$ 1,091	$ 824