Asset Quality (Details 4) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Past due loans including current loans
Current	$ 47,971		$ 47,041
30 to 59 Days Past Due	300		315
60 to 89 Days Past Due	120		158
90 and Greater Days Past Due	169		153
Nonperforming Loans	666	727	885
Total Past Due and Nonperforming Loans	1,255		1,511
Total Loans	49,226		48,552
Commercial, financial and agricultural [Member]
Past due loans including current loans
Current	19,559		16,138
30 to 59 Days Past Due	25		46
60 to 89 Days Past Due	16		13
90 and Greater Days Past Due	19		22
Nonperforming Loans	168		221
Total Past Due and Nonperforming Loans	228		302
Total Loans	19,787		16,440
Commercial real estate: Commercial Mortgage [Member]
Past due loans including current loans
Current	7,532		8,459
30 to 59 Days Past Due	7		36
60 to 89 Days Past Due	11		37
90 and Greater Days Past Due	82		29
Nonperforming Loans	175		245
Total Past Due and Nonperforming Loans	275		347
Total Loans	7,807		8,806
Construction [Member]
Past due loans including current loans
Current	1,170		1,623
30 to 59 Days Past Due	19		40
60 to 89 Days Past Due	7		14
90 and Greater Days Past Due	11		22
Nonperforming Loans	66		146
Total Past Due and Nonperforming Loans	103		222
Total Loans	1,273		1,845
Commercial Real Estate Loans [Member]
Past due loans including current loans
Current	8,702		10,082
30 to 59 Days Past Due	26		76
60 to 89 Days Past Due	18		51
90 and Greater Days Past Due	93		51
Nonperforming Loans	241		391
Total Past Due and Nonperforming Loans	378		569
Total Loans	9,080		10,651
Commercial Lease Financing [Member]
Past due loans including current loans
Current	5,570		6,054
30 to 59 Days Past Due	126		53
60 to 89 Days Past Due	22		21
90 and Greater Days Past Due	15		37
Nonperforming Loans	22		42
Total Past Due and Nonperforming Loans	185		153
Total Loans	5,755		6,207
Commercial Loans [Member]
Past due loans including current loans
Current	33,831		32,274
30 to 59 Days Past Due	177		175
60 to 89 Days Past Due	56		85
90 and Greater Days Past Due	127		110
Nonperforming Loans	431		654
Total Past Due and Nonperforming Loans	791		1,024
Total Loans	34,622		33,298
Real estate - residential mortgage [Member]
Past due loans including current loans
Current	1,852		1,676
30 to 59 Days Past Due	20		22
60 to 89 Days Past Due	8		12
90 and Greater Days Past Due	5		9
Nonperforming Loans	82		84
Total Past Due and Nonperforming Loans	115		127
Total Loans	1,967		1,803
Home Equity Key Community Bank [Member]
Past due loans including current loans
Current	8,941		9,211
30 to 59 Days Past Due	53		60
60 to 89 Days Past Due	34		34
90 and Greater Days Past Due	16		17
Nonperforming Loans	109		99
Total Past Due and Nonperforming Loans	212		210
Total Loans	9,153		9,421
Home Equity Other [Member]
Past due loans including current loans
Current	476		591
30 to 59 Days Past Due	9		11
60 to 89 Days Past Due	6		7
90 and Greater Days Past Due	4		5
Nonperforming Loans	12		13
Total Past Due and Nonperforming Loans	31		36
Total Loans	507		627
Home Equity Loans [Member]
Past due loans including current loans
Current	9,417		9,802
30 to 59 Days Past Due	62		71
60 to 89 Days Past Due	40		41
90 and Greater Days Past Due	20		22
Nonperforming Loans	121		112
Total Past Due and Nonperforming Loans	243		246
Total Loans	9,660		10,048
Consumer Marine [Member]
Past due loans including current loans
Current	1,576		2,030
30 to 59 Days Past Due	30		34
60 to 89 Days Past Due	11		14
90 and Greater Days Past Due	7		3
Nonperforming Loans	30		31
Total Past Due and Nonperforming Loans	78		82
Total Loans	1,654		2,112
Consumer Others [Member]
Past due loans including current loans
Current	106		144
30 to 59 Days Past Due	2		3
60 to 89 Days Past Due	1		1
90 and Greater Days Past Due	1		1
Nonperforming Loans	1		1
Total Past Due and Nonperforming Loans	5		6
Total Loans	111		150
Consumer other - Key Community Bank [Member]
Past due loans including current loans
Current	1,189		1,115
30 to 59 Days Past Due	9		10
60 to 89 Days Past Due	4		5
90 and Greater Days Past Due	9		8
Nonperforming Loans	1		3
Total Past Due and Nonperforming Loans	23		26
Total Loans	1,212		1,141
Consumer Other [Member]
Past due loans including current loans
Current	1,682		2,174
30 to 59 Days Past Due	32		37
60 to 89 Days Past Due	12		15
90 and Greater Days Past Due	8		4
Nonperforming Loans	31		32
Total Past Due and Nonperforming Loans	83		88
Total Loans	1,765		2,262
Consumer Loans [Member]
Past due loans including current loans
Current	14,140		14,767
30 to 59 Days Past Due	123		140
60 to 89 Days Past Due	64		73
90 and Greater Days Past Due	42		43
Nonperforming Loans	235		231
Total Past Due and Nonperforming Loans	464		487
Total Loans	$ 14,604		$ 15,254