Acquisitions and Discontinued Operations - Components of Assets and Liabilities from Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013		Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	$ 409		$ 617		$ 621		$ 584
Total assets	4,427	[1]	4,572	[1]	5,182	[1]
Total liabilities	1,819	[1]	1,854	[1]	2,176	[1]
Seller note	14		30		46
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and due from banks	19		20		23
Accrued expense and other liabilities	3				25
Segment, Discontinued Operations [Member] | Seller Note [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Seller note	28		29
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
Total assets	28		29		44
Accrued expense and other liabilities					24
Total liabilities					24
Accrued income and other assets					43
Segment, Discontinued Operations [Member] | Victory Capital Management [Member] | Seller Note [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Seller note	28		29
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	19		20		22
Total assets	19		20		22
Accrued expense and other liabilities	3				1
Total liabilities	$ 3				$ 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.