Asset Quality (Details 9) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	$ 1,604	$ 2,534	$ 1,629
Provisions	(59)	640
Charge-offs	(715)	(1,822)	(2,396)
Recoveries	174	252	139
Balance at end of period - continuing operations	1,004	1,604	2,534
Discontinued Operations, Beginning Balance	114	157
Provision, Discontinued Operations	113	78
Charge-offs, Discontinued Operations	(138)	(129)
Recoveries, Discontinued Operations	15	8
Discontinued Operations, Ending Balance	104	114	157
Financing Receivable Allowance For Credit Losses Total ALLL Including Discontinued Operations, Beginning Balance	1,718	2,691
Provisions, Total ALLL - Including Discontinued Operations	54	718
Charge-offs, Total ALLL - Including Discontinued Operations	(853)	(1,951)
Recoveries, Total ALLL - Including Discontinued Operations	189	260
Financing Receivable Allowance For Credit Losses Total ALLL Including Discontinued Operations, Ending Balance	1,108	1,718	2,691
Commercial, Financial and Agricultural [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	485	796
Provisions	(32)	167
Charge-offs	(169)	(565)
Recoveries	50	87
Balance at end of period - continuing operations	334	485
Commercial real estate: Commercial Mortgage [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	416	578
Provisions	(41)	168
Charge-offs	(113)	(360)
Recoveries	10	30
Balance at end of period - continuing operations	272	416
Commercial real estate: Construction [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	145	418
Provisions	(26)	63
Charge-offs	(83)	(380)
Recoveries	27	44
Balance at end of period - continuing operations	63	145
Commercial Lease Financing [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	175	280
Provisions	(80)	(42)
Charge-offs	(42)	(88)
Recoveries	25	25
Balance at end of period - continuing operations	78	175
Commercial [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	1,221	2,072
Provisions	(179)	356
Charge-offs	(407)	(1,393)
Recoveries	112	186
Balance at end of period - continuing operations	747	1,221
Real estate - residential mortgage [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	49	30
Provisions	14	53
Charge-offs	(29)	(36)
Recoveries	3	2
Balance at end of period - continuing operations	37	49
Home Equity Key Community Bank [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	120	130
Provisions	72	106
Charge-offs	(100)	(123)
Recoveries	11	7
Balance at end of period - continuing operations	103	120
Home Equity Other [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	57	78
Provisions	13	38
Charge-offs	(45)	(62)
Recoveries	4	3
Balance at end of period - continuing operations	29	57
Home Equity [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	177	208
Provisions	85	144
Charge-offs	(145)	(185)
Recoveries	15	10
Balance at end of period - continuing operations	132	177
Consumer Other - Key Community Bank [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	57	73
Provisions	21	41
Charge-offs	(45)	(64)
Recoveries	8	7
Balance at end of period - continuing operations	41	57
Consumer Marine [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	89	140
Provisions	5	35
Charge-offs	(80)	(129)
Recoveries	32	43
Balance at end of period - continuing operations	46	89
Consumer Others [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	11	11
Provisions	(5)	11
Charge-offs	(9)	(15)
Recoveries	4	4
Balance at end of period - continuing operations	1	11
Consumer Other - Key Corporate Bank [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	100	151
Provisions		46
Charge-offs	(89)	(144)
Recoveries	36	47
Balance at end of period - continuing operations	47	100
Consumer Loans [Member]
Changes in Allowance for loan and lease losses by loan category
Balance at beginning of period - continuing operations	383	462
Provisions	120	284
Charge-offs	(308)	(429)
Recoveries	62	66
Balance at end of period - continuing operations	$ 257	$ 383