Earnings Per Common Share (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
EARNINGS
Income (loss) from continuing operations	$ 205		$ 282
Less: Net income (loss) attributable to noncontrolling interests			8
Income (loss) from continuing operations attributable to Key	205		274
Income (loss) from continuing operations attributable to Key common shareholders	199		184
Income (loss) from discontinued operations, net of taxes	(5)		(11)
Net income (loss) attributable to Key common shareholders	194		173
WEIGHTED-AVERAGE COMMON SHARES
Weighted-average common shares outstanding (000)	949,342	[1]	881,894	[1]
Effect of dilutive convertible preferred stock, common stock options and other stock awards (000)	4,629		5,942
Weighted-average common shares and potential common shares outstanding (000)	953,971		887,836
EARNINGS PER COMMON SHARE
Income (loss) from continuing operations attributable to Key common shareholders	$ 0.21		$ 0.21
Income (loss) from discontinued operations, net of taxes	$ (0.01)		$ (0.01)
Net income (loss) attributable to Key common shareholders	$ 0.20		$ 0.20
Income (loss) from continuing operations attributable to Key common shareholders - assuming dilution	$ 0.21		$ 0.21
Income (loss) from discontinued operations, net of taxes	$ (0.01)		$ (0.01)
Net income (loss) attributable to Key common shareholders - assuming dilution	$ 0.20	[2]	$ 0.19	[2]
Series A Preferred Stock [Member]
EARNINGS
Less: Dividends on Series A Preferred Stock	6		6
Series B Preferred Stock [Member]
EARNINGS
Less: Dividends on Series A Preferred Stock			31
Amortization of discount on Series B Preferred Stock			$ 53

[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.

[2] Assumes conversion of stock options and/or Preferred Series A, as applicable.