Acquisitions and Discontinued Operations - Components of Assets and Liabilities of Austin Capital Management (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	$ 585		$ 694		$ 278	$ 471
Total assets	5,254	[1]	5,860	[1]
Total liabilities	2,182	[1]	2,550	[1]
Segment, discontinued operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	22		31
Segment, discontinued operations [Member] | Austin Capital Management [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	22		31
Total assets	22		31
Accrued expense and other liabilities	1
Total liabilities	$ 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.