Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Federal
Current	$ 51	$ 301	$ 457	$ 455
Deferred	317	(123)	273	(143)
Federal income tax	368	178	730	312
State
Current	62	32	72	61
Deferred	28	(11)	22	(13)
State income tax	90	21	94	48
Total income tax provision	458	199	824	360
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	573	333	1,061	622
State income tax, at statutory rates, net of federal tax benefit	58	14	61	31
Tax effect of
Tax credits, net of related expenses	(108)	(110)	(195)	(210)
Tax-exempt income	(57)	(53)	(113)	(105)
Noncontrolling interests	8	5	14	7
Other items	(16)	10	(4)	15
Applicable income taxes	458	199	824	360
Income Taxes (Textuals) [Abstract]
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Net deferred tax assets (liabilities)	$ 711		$ 711		$ 424