Condensed Financial Information of the Parent Company (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Dividends from subsidiaries
Total interest income	$ 2,889	$ 3,408	$ 3,795
EXPENSE
Interest on long-term debt with subsidiary trusts	216	206	275
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	1,345	793	(2,298)
Income taxes	369	186	(1,035)
NET INCOME (LOSS)	932	584	(1,311)
Less: Net income (loss) attributable to noncontrolling interests	12	30	24
NET INCOME (LOSS) ATTRIBUTABLE TO KEY	920	554	(1,335)
Parent Company [Member]
Dividends from subsidiaries
Interest income from subsidiaries	67	99	114
Other income	18	32	89
Total interest income	430	156	204
EXPENSE
Interest on long-term debt with subsidiary trusts	53	54	77
Interest on other borrowed funds	89	67	67
Personnel and other expense	178	121	172
Total expense	320	242	316
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	110	(86)	(112)
Income taxes	73	38	38
Income (loss) before equity in net income (loss) less dividends from subsidiaries	183	(48)	(74)
Equity in net income (loss) less dividends from subsidiaries	749	632	(1,237)
NET INCOME (LOSS)	932	584	(1,311)
Less: Net income (loss) attributable to noncontrolling interests	12	30	24
NET INCOME (LOSS) ATTRIBUTABLE TO KEY	920	554	(1,335)
Parent Company [Member] | Nonbank Subsidiaries [Member]
Dividends from subsidiaries
Total dividend income	$ 345	$ 25	$ 1