Asset Quality (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Past due loans including current loans
Current	$ 48,243	$ 48,324
30 to 59 Days Past Due	306	330
60 to 89 Days Past Due	135	146
90 and Greater Days Past Due	164	239
Nonperforming Loans	727	1,068
Total Past Due and Nonperforming Loans	1,332	1,783
Total Loans	49,575	50,107
Commercial, financial and agricultural [Member]
Past due loans including current loans
Current	19,136	16,049
30 to 59 Days Past Due	25	35
60 to 89 Days Past Due	17	22
90 and Greater Days Past Due	12	93
Nonperforming Loans	188	242
Total Past Due and Nonperforming Loans	242	392
Total Loans	19,378	16,441
Commercial real estate: Commercial Mortgage [Member]
Past due loans including current loans
Current	7,680	9,158
30 to 59 Days Past Due	57	33
60 to 89 Days Past Due	18	16
90 and Greater Days Past Due	64	40
Nonperforming Loans	218	255
Total Past Due and Nonperforming Loans	357	344
Total Loans	8,037	9,502
Construction [Member]
Past due loans including current loans
Current	1,225	1,796
30 to 59 Days Past Due	6	27
60 to 89 Days Past Due	1	4
90 and Greater Days Past Due	26	38
Nonperforming Loans	54	241
Total Past Due and Nonperforming Loans	87	310
Total Loans	1,312	2,106
Commercial Real Estate Loans [Member]
Past due loans including current loans
Current	8,905	10,954
30 to 59 Days Past Due	63	60
60 to 89 Days Past Due	19	20
90 and Greater Days Past Due	90	78
Nonperforming Loans	272	496
Total Past Due and Nonperforming Loans	444	654
Total Loans	9,349	11,608
Commercial Lease Financing [Member]
Past due loans including current loans
Current	5,920	6,316
30 to 59 Days Past Due	71	64
60 to 89 Days Past Due	21	17
90 and Greater Days Past Due	16	10
Nonperforming Loans	27	64
Total Past Due and Nonperforming Loans	135	155
Total Loans	6,055	6,471
Commercial Loans [Member]
Past due loans including current loans
Current	33,961	33,319
30 to 59 Days Past Due	159	159
60 to 89 Days Past Due	57	59
90 and Greater Days Past Due	118	181
Nonperforming Loans	487	802
Total Past Due and Nonperforming Loans	821	1,201
Total Loans	34,782	34,520
Real estate - residential mortgage [Member]
Past due loans including current loans
Current	1,816	1,698
30 to 59 Days Past Due	21	25
60 to 89 Days Past Due	13	12
90 and Greater Days Past Due	9	11
Nonperforming Loans	87	98
Total Past Due and Nonperforming Loans	130	146
Total Loans	1,946	1,844
Home Equity Key Community Bank [Member]
Past due loans including current loans
Current	9,004	9,282
30 to 59 Days Past Due	64	69
60 to 89 Days Past Due	34	37
90 and Greater Days Past Due	19	24
Nonperforming Loans	108	102
Total Past Due and Nonperforming Loans	225	232
Total Loans	9,229	9,514
Home Equity Other [Member]
Past due loans including current loans
Current	497	615
30 to 59 Days Past Due	14	17
60 to 89 Days Past Due	8	10
90 and Greater Days Past Due	4	6
Nonperforming Loans	12	18
Total Past Due and Nonperforming Loans	38	51
Total Loans	535	666
Home Equity Loans [Member]
Past due loans including current loans
Current	9,501	9,897
30 to 59 Days Past Due	78	86
60 to 89 Days Past Due	42	47
90 and Greater Days Past Due	23	30
Nonperforming Loans	120	120
Total Past Due and Nonperforming Loans	263	283
Total Loans	9,764	10,180
Consumer Marine [Member]
Past due loans including current loans
Current	1,678	2,117
30 to 59 Days Past Due	37	48
60 to 89 Days Past Due	15	20
90 and Greater Days Past Due	5	7
Nonperforming Loans	31	42
Total Past Due and Nonperforming Loans	88	117
Total Loans	1,766	2,234
Consumer Others [Member]
Past due loans including current loans
Current	119	154
30 to 59 Days Past Due	2	3
60 to 89 Days Past Due	2	2
90 and Greater Days Past Due	1	1
Nonperforming Loans	1	2
Total Past Due and Nonperforming Loans	6	8
Total Loans	125	162
Consumer other - Key Community Bank [Member]
Past due loans including current loans
Current	1,168	1,139
30 to 59 Days Past Due	9	9
60 to 89 Days Past Due	6	6
90 and Greater Days Past Due	8	9
Nonperforming Loans	1	4
Total Past Due and Nonperforming Loans	24	28
Total Loans	1,192	1,167
Consumer Other [Member]
Past due loans including current loans
Current	1,797	2,271
30 to 59 Days Past Due	39	51
60 to 89 Days Past Due	17	22
90 and Greater Days Past Due	6	8
Nonperforming Loans	32	44
Total Past Due and Nonperforming Loans	94	125
Total Loans	1,891	2,396
Consumer Loans [Member]
Past due loans including current loans
Current	14,282	15,005
30 to 59 Days Past Due	147	171
60 to 89 Days Past Due	78	87
90 and Greater Days Past Due	46	58
Nonperforming Loans	240	266
Total Past Due and Nonperforming Loans	511	582
Total Loans	$ 14,793	$ 15,587