Asset Quality (Details 9) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	$ 1,004	$ 1,604
Provisions	41	(39)
Charge-offs	(132)	(232)
Recoveries	31	39
Balance at end of period - continuing operations	944	1,372
Discontinued Operations, Beginning Balance	104	114
Provision, Discontinued Operations	5	32
Charge-offs, Discontinued Operations	(23)	(38)
Recoveries, Discontinued Operations	4	3
Discontinued Operations, Ending Balance	90	111
Financing Receivable Allowance For Credit Losses Total ALLL Including Discontinued Operations, Beginning Balance	1,108	1,718
Provisions, Total ALLL - Including Discontinued Operations	46	(7)
Charge-offs, Total ALLL - Including Discontinued Operations	(155)	(270)
Recoveries, Total ALLL - Including Discontinued Operations	35	42
Financing Receivable Allowance For Credit Losses Total ALLL Including Discontinued Operations, Ending Balance	1,034	1,483
Commercial, Financial and Agricultural [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	334	485
Provisions	(3)	(34)
Charge-offs	(26)	(42)
Recoveries	11	10
Balance at end of period - continuing operations	316	419
Commercial real estate: Commercial Mortgage [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	272	416
Provisions	12	13
Charge-offs	(23)	(46)
Recoveries	2	3
Balance at end of period - continuing operations	263	386
Commercial real estate: Construction [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	63	145
Provisions	3	2
Charge-offs	(11)	(35)
Recoveries	1	5
Balance at end of period - continuing operations	56	117
Commercial Lease Financing [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	78	175
Provisions	(10)	(32)
Charge-offs	(4)	(17)
Recoveries	4	6
Balance at end of period - continuing operations	68	132
Commercial [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	747	1,221
Provisions	2	(51)
Charge-offs	(64)	(140)
Recoveries	18	24
Balance at end of period - continuing operations	703	1,054
Real estate - residential mortgage [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	37	49
Provisions	4
Charge-offs	(6)	(10)
Recoveries	1	1
Balance at end of period - continuing operations	36	40
Home Equity Key Community Bank [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	103	120
Provisions	14	15
Charge-offs	(25)	(25)
Recoveries	2	1
Balance at end of period - continuing operations	94	111
Home Equity Other [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	29	57
Provisions	6	2
Charge-offs	(8)	(15)
Recoveries	1	1
Balance at end of period - continuing operations	28	45
Home Equity [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	132	177
Provisions	20	17
Charge-offs	(33)	(40)
Recoveries	3	2
Balance at end of period - continuing operations	122	156
Consumer Other - Key Community Bank [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	41	57
Provisions	5	3
Charge-offs	(10)	(12)
Recoveries	1	2
Balance at end of period - continuing operations	37	50
Consumer Marine [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	46	89
Provisions	9	(2)
Charge-offs	(17)	(27)
Recoveries	7	8
Balance at end of period - continuing operations	45	68
Consumer Others [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	1	11
Provisions	1	(6)
Charge-offs	(2)	(3)
Recoveries	1	2
Balance at end of period - continuing operations	1	4
Consumer Other - Key Corporate Bank [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	47	100
Provisions	10	(8)
Charge-offs	(19)	(30)
Recoveries	8	10
Balance at end of period - continuing operations	46	72
Consumer Loans [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	257	383
Provisions	39	12
Charge-offs	(68)	(92)
Recoveries	13	15
Balance at end of period - continuing operations	$ 241	$ 318