Line of Business Results (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Supplementary information (Key Corporate Bank lines of business)
Provision (credit) for loan and lease losses	$ (60)	$ 638		$ 3,159
Noninterest expense	2,790	3,034		3,554
Net income (loss) attributable to Key	920	554		(1,335)
Real Estate Capital and Corporate Banking Services [Member]
Supplementary information (Key Corporate Bank lines of business)
Total revenue (TE)	638	661		580
Provision (credit) for loan and lease losses	(109)	34		1,492
Noninterest expense	246	388	[1]	425
Net income (loss) attributable to Key	316	152		(852)
Average loans and leases	7,702	10,864		14,602
Average loans held for sale	190	178		204
Average deposits	7,724	9,731		10,398
Net loan charge-offs	119	509		1,042
Net loan charge-offs to average loans	1.55%	4.69%		7.14%
Nonperforming assets at year end	209	442		1,094
Return on average allocated equity	26.20%	8.13%		(37.19%)
Average full-time equivalent employees	920	901		968
Equipment Finance [Member]
Supplementary information (Key Corporate Bank lines of business)
Total revenue (TE)	256	250		253
Provision (credit) for loan and lease losses	(79)	(15)		223
Noninterest expense	190	200		254
Net income (loss) attributable to Key	91	41		(140)
Average loans and leases	4,617	4,556		4,925
Average loans held for sale	5	5		11
Average deposits	9	4		8
Net loan charge-offs	11	67		102
Net loan charge-offs to average loans	0.24%	1.47%		2.07%
Nonperforming assets at year end	41	68		122
Return on average allocated equity	29.35%	11.65%		(36.36%)
Average full-time equivalent employees	515	544		621
Institutional and Capital Markets [Member]
Supplementary information (Key Corporate Bank lines of business)
Total revenue (TE)	675	724		730
Provision (credit) for loan and lease losses	(10)	(47)		111
Noninterest expense	441	410		570
Net income (loss) attributable to Key	158	231		5
Average loans and leases	5,083	4,950		7,708
Average loans held for sale	107	131		203
Average deposits	3,062	2,500		2,303
Net loan charge-offs	8	31		116
Net loan charge-offs to average loans	0.16%	0.63%		1.50%
Nonperforming assets at year end	$ 44	$ 65		$ 110
Return on average allocated equity	21.41%	26.07%		0.46%
Average full-time equivalent employees	796	747		764

[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.