Condensed Financial Information of the Parent Company (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
ASSETS
Loans, net of allowance	$ 48,571		$ 48,503
Investment in Subsidiaries
Trust accrued income and other assets at fair value	3,077	[1]	3,876	[1]
Total assets	88,785		91,843
LIABILITIES
Accrued expense and other liabilities	1,763		1,931
Long-term debt due to
Total long-term debt	9,520		10,592
Total liabilities	78,863		80,469
Key shareholders' equity	9,905		11,117
Total liabilities and equity	88,785		91,843
Parent Company [Member]
ASSETS
Cash and interest-bearing deposits	2,114		3,293
Loans, net of allowance	713		1,669
Investment in Subsidiaries
Total investment in subsidiaries	10,803		10,017
Trust accrued income and other assets at fair value	1,153		940
Total assets	14,783		15,919
LIABILITIES
Accrued expense and other liabilities	579		621
Long-term debt due to
Total long-term debt	4,299		4,181
Total liabilities	4,878		4,802
Key shareholders' equity	9,905		11,117
Total liabilities and equity	14,783		15,919
Parent Company [Member] | Bank [Member]
Investment in Subsidiaries
Equity Method Investments	10,114		9,388
Parent Company [Member] | Nonbank Subsidiaries [Member]
Investment in Subsidiaries
Equity Method Investments	713		629
Parent Company [Member] | Subsidiaries [Member]
Long-term debt due to
Total long-term debt	1,225		1,948
Parent Company [Member] | Unaffiliated Companies [Member]
Long-term debt due to
Total long-term debt	$ 3,074		$ 2,233

[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.