Acquisitions and Discontinued Operations - Components of Assets and Liabilities from Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012		Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	$ 696		$ 584		$ 716		$ 693
Total assets	5,084	[1]	5,282	[1]	5,545	[1]
Total liabilities	2,169	[1]	2,220	[1]	2,428	[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		23		23
Accrued expense and other liabilities	30		39		27
Segment, Discontinued Operations [Member] | Victory Capital Management [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	1		1		1
Accrued income and other assets	35		27		11
Total assets	36		28		12
Accrued expense and other liabilities	30		38		27
Total liabilities	30		38		27
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	21		22		22
Total assets	21		22		22
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.