Asset Quality (Details 10) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	$ 51	$ 58
Collectively Evaluated for Impairment Allowance	953	1,546
Loans Outstanding	49,575	50,107
Individually Evaluated for Impairment Outstanding	388	621
Collectively Evaluated for Impairment, Outstanding	49,187	49,486
Individually Evaluated for Impairment Allowance, Discontinued Operations	0	0
Collectively Evaluated for Impairment Allowance, Discontinued Operations	104	114
Loans Outstanding, Discontinued Operations	5,812	6,451
Individually Evaluated for Impairment Outstanding, Discontinued Operations	0	0
Collectively Evaluated for Impairment Outstanding, Discontinued Operations	5,812	6,451
Individually Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	51	58
Collectively Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	1,057	1,660
Loans Outstanding Total ALLL - Including Discontinued Operations	55,387	56,558
Individually Evaluated for Impairment Outstanding Total ALLL - Including Discontinued Operations	388	621
Collectively Evaluated for Impairment Outstanding Total ALLL - Including Discontinued Operations	54,999	55,937
Commercial, Financial and Agricultural [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	26	26
Collectively Evaluated for Impairment Allowance	308	459
Loans Outstanding	19,378	16,441
Individually Evaluated for Impairment Outstanding	150	150
Collectively Evaluated for Impairment, Outstanding	19,228	16,291
Commercial real estate: Commercial Mortgage [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	21	18
Collectively Evaluated for Impairment Allowance	251	398
Loans Outstanding	8,037	9,502
Individually Evaluated for Impairment Outstanding	196	248
Collectively Evaluated for Impairment, Outstanding	7,841	9,254
Commercial real estate: Construction [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	4	7
Collectively Evaluated for Impairment Allowance	59	138
Loans Outstanding	1,312	2,106
Individually Evaluated for Impairment Outstanding	42	211
Collectively Evaluated for Impairment, Outstanding	1,270	1,895
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	25	25
Collectively Evaluated for Impairment Allowance	310	536
Loans Outstanding	9,349	11,608
Individually Evaluated for Impairment Outstanding	238	459
Collectively Evaluated for Impairment, Outstanding	9,111	11,149
Commercial Lease Financing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	7
Collectively Evaluated for Impairment Allowance	78	168
Loans Outstanding	6,055	6,471
Individually Evaluated for Impairment Outstanding	0	12
Collectively Evaluated for Impairment, Outstanding	6,055	6,459
Commercial [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	51	58
Collectively Evaluated for Impairment Allowance	696	1,163
Loans Outstanding	34,782	34,520
Individually Evaluated for Impairment Outstanding	388	621
Collectively Evaluated for Impairment, Outstanding	34,394	33,899
Real estate - residential mortgage [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	37	49
Loans Outstanding	1,946	1,844
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	1,946	1,844
Home Equity Key Community Bank [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	103	120
Loans Outstanding	9,229	9,514
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	9,229	9,514
Home Equity Other [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	29	57
Loans Outstanding	535	666
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	535	666
Home Equity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	132	177
Loans Outstanding	9,764	10,180
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	9,764	10,180
Consumer Other - Key Community Bank [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	41	57
Loans Outstanding	1,192	1,167
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	1,192	1,167
Consumer Marine [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	46	89
Loans Outstanding	1,766	2,234
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	1,766	2,234
Consumer Others [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	1	11
Loans Outstanding	125	162
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	125	162
Consumer Other - Key Corporate Bank [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	47	100
Loans Outstanding	1,891	2,396
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	1,891	2,396
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	257	383
Loans Outstanding	14,793	15,587
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	$ 14,793	$ 15,587