Line of Business Results (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Supplementary information (Key Corporate Bank lines of business)
Provision (credit) for loan and lease losses	$ 42	$ (40)
Noninterest expense	703	701
Net income (loss) attributable to Key	200	263
Real Estate Capital and Corporate Banking Services [Member]
Supplementary information (Key Corporate Bank lines of business)
Total revenue (TE)	161	168
Provision (credit) for loan and lease losses		9
Noninterest expense	59	69	[1]
Net income (loss) attributable to Key	64	57
Average loans and leases	7,699	8,583
Average loans held for sale	291	140
Average deposits	8,221	8,611
Net loan charge-offs	16	65
Net loan charge-offs to average loans	0.84%	3.07%
Nonperforming assets at year end	173	334
Return on average allocated equity	27.56%	15.56%
Average full-time equivalent employees	951	882
Equipment Finance [Member]
Supplementary information (Key Corporate Bank lines of business)
Total revenue (TE)	64	63
Provision (credit) for loan and lease losses	(2)	(26)
Noninterest expense	37	52
Net income (loss) attributable to Key	18	23
Average loans and leases	4,779	4,621
Average loans held for sale	24	4
Average deposits	8	6
Net loan charge-offs	5	10
Net loan charge-offs to average loans	0.42%	0.88%
Nonperforming assets at year end	28	44
Return on average allocated equity	26.71%	27.04%
Average full-time equivalent employees	469	521
Institutional and Capital Markets [Member]
Supplementary information (Key Corporate Bank lines of business)
Total revenue (TE)	176	175
Provision (credit) for loan and lease losses	15	(4)
Noninterest expense	135	107
Net income (loss) attributable to Key	18	46
Average loans and leases	6,106	4,473
Average loans held for sale	194	131
Average deposits	3,327	2,665
Net loan charge-offs	4
Net loan charge-offs to average loans	0.26%
Nonperforming assets at year end	$ 36	$ 49
Return on average allocated equity	10.28%	24.51%
Average full-time equivalent employees	834	752

[1] The assets of the VIEs can only be used by the particular VIE and there is no recourse to Key with respect to the liabilities of the consolidated LIHTC or education loan securitization trust VIEs.