Line of Business Results (Details 1) (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 Community Banking 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
Regional Banking [Member]
Supplementary information ( Key Community Banking lines of business)
Total revenue (TE)	450	489	897	974
Provision (credit) for loan and lease losses	63	57	80	172
Noninterest expense	400	409	799	816
Net income (loss) attributable to Key	6	27	38	16
Average loans and leases	17,495	18,404	17,546	18,577
Average loans held for sale	42	69	56	75
Average deposits	41,710	45,219	41,948	45,698
Net loan charge-offs	65	82	127	179
Net loan charge-offs to average loans	1.49%	1.79%	1.46%	1.94%
Nonperforming assets at year end	302	339	302	339
Return on average allocated equity, Total	1.08%	4.65%	3.41%	1.39%
Average full-time equivalent employees	8,138	7,886	8,074	7,859
Commercial Banking [Member]
Supplementary information ( Key Community Banking lines of business)
Total revenue (TE)	109	113	226	222
Provision (credit) for loan and lease losses	16	64	10	91
Noninterest expense	48	43	93	88
Net income (loss) attributable to Key	28	4	77	27
Average loans and leases	8,747	8,813	8,731	8,914
Average loans held for sale	21	1	26	1
Average deposits	6,009	5,187	5,964	5,224
Net loan charge-offs	14	66	28	85
Net loan charge-offs to average loans	0.64%	3.00%	0.65%	1.92%
Nonperforming assets at year end	$ 153	$ 222	$ 153	$ 222
Return on average allocated equity, Total	11.59%	1.30%	15.59%	4.38%
Average full-time equivalent employees	366	355	367	353