Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Currently payable:
Federal	$ 90	$ 127	$ (97)
State	(31)	(21)	(60)
Total currently payable	59	106	(157)
Deferred:
Federal	280	51	(806)
State	30	29	(72)
Total deferred	310	80	(878)
Income tax (benefit) expense	369	186	(1,035)
Significant components of deferred tax assets and liabilities, included in "accrued income and other assets" and "accrued expense and other liabilities"
Allowance for loan and lease losses	409	701
Employee benefits	228	202
Federal credit carryforwards	442	390
Net operating losses	12	71
Other	298	381
Total deferred tax assets	1,389	1,745
Leasing transactions	985	1,033
Net unrealized securities gains	199	158
Other	113	124
Total deferred tax liabilities	1,297	1,315
Net deferred tax assets (liabilities)	$ 92	$ 430