Line of Business Results (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Supplementary information ( Key Corporate Bank lines of business)
Provision (credit) for loan and lease losses	$ (8)	$ 228	$ (48)	$ 641
Noninterest expense	680	769	1,381	1,554
Net income (loss) attributable to Key	240	70	503	15
Real Estate Capital and Corporate Banking Services [Member]
Supplementary information ( Key Corporate Bank lines of business)
Total revenue (TE)	154	173	319	314
Provision (credit) for loan and lease losses	(49)	77	(39)	222
Noninterest expense	50	97	117	217
Net income (loss) attributable to Key	95		152	(78)
Average loans and leases	7,713	11,466	8,146	11,901
Average loans held for sale	229	194	185	154
Average deposits	7,371	9,728	7,987	9,683
Net loan charge-offs	26	142	91	349
Net loan charge-offs to average loans	1.35%	4.97%	2.25%	5.91%
Nonperforming assets at year end	245	867	245	867
Return on average allocated equity, Total	30.66%		22.42%	(7.77%)
Average full-time equivalent employees	902	901	892	911
Equipment Finance [Member]
Supplementary information ( Key Corporate Bank lines of business)
Total revenue (TE)	63	61	127	122
Provision (credit) for loan and lease losses	(30)	10	(56)	14
Noninterest expense	45	49	97	94
Net income (loss) attributable to Key	30	1	54	9
Average loans and leases	4,545	4,478	4,583	4,525
Average loans held for sale		16	2	9
Average deposits	12	5	9	5
Net loan charge-offs	2	18	12	36
Net loan charge-offs to average loans	0.18%	1.61%	0.53%	1.60%
Nonperforming assets at year end	39	106	39	106
Return on average allocated equity, Total	37.02%	1.15%	34.24%	5.08%
Average full-time equivalent employees	511	549	516	556
Institutional and Capital Markets [Member]
Supplementary information ( Key Corporate Bank lines of business)
Total revenue (TE)	172	172	346	343
Provision (credit) for loan and lease losses	3	12	(2)	24
Noninterest expense	111	103	220	210
Net income (loss) attributable to Key	38	37	82	71
Average loans and leases	4,910	5,005	4,692	5,265
Average loans held for sale	73	171	102	148
Average deposits	2,812	2,658	2,740	2,618
Net loan charge-offs	1	13	1	39
Net loan charge-offs to average loans	0.08%	1.04%	0.04%	1.49%
Nonperforming assets at year end	$ 55	$ 116	$ 55	$ 116
Return on average allocated equity, Total	20.11%	15.46%	21.56%	14.70%
Average full-time equivalent employees	778	725	765	727