Acquisition and Discontinued Operations (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011		Dec. 31, 2010
Components of Income (Loss) from Discontinued Operations, Net of Taxes, of Subsidiary
Noninterest income	$ 472		$ 457
Noninterest expense	703		701
Income taxes	75		111
Income (loss) from discontinued operations, net of taxes	(5)		(11)
Components of Assets and Liabilities of Subsidiary
Cash and due from banks	416		540		694		278
Accrued income and other assets (including $87 of consolidated LIHTC guaranteed funds VIEs, see Note 9)(a)	3,091	[1]	3,758	[1]	3,077	[1]
Total assets	5,768	[1]	6,393	[1]	5,860	[1]
Total liabilities	2,549	[1]	2,929	[1]	2,550	[1]
Community Bank [Member]
Components of Income (Loss) from Discontinued Operations, Net of Taxes, of Subsidiary
Noninterest income	175		187
Income taxes	13		26
Income (loss) from discontinued operations, net of taxes
Segment, Discontinued Operations [Member]
Components of Income (Loss) from Discontinued Operations, Net of Taxes, of Subsidiary
Noninterest income	18		9
Noninterest expense	17		12
Income (loss) before income taxes	(8)		(17)
Income taxes	(3)		(6)
Income (loss) from discontinued operations, net of taxes	(5)		(11)
Components of Assets and Liabilities of Subsidiary
Cash and due from banks	30		33		31
Total liabilities	2,549		2,929		2,550
Segment, Discontinued Operations [Member] | Austin Capital Management [Member]
Components of Income (Loss) from Discontinued Operations, Net of Taxes, of Subsidiary
Noninterest income			1
Noninterest expense	8		1
Income (loss) before income taxes	(8)
Income taxes	(3)
Income (loss) from discontinued operations, net of taxes	(5)
Components of Assets and Liabilities of Subsidiary
Cash and due from banks	30		33		31
Accrued income and other assets (including $87 of consolidated LIHTC guaranteed funds VIEs, see Note 9)(a)	1
Total assets	31		33		31
Accrued expense and other liabilities	7		1
Total liabilities	$ 7		$ 1

[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.