Acquisitions and Discontinued Operations - Components of Assets and Liabilities of Education Lending Business (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	$ 143		$ 147		$ 154
Loans, net of unearned income of ($6), ($6), and ($5)	55,445		54,457		52,574
Less: Allowance for loan and lease losses	834		848		893
Net loans	54,611		53,609		51,681
Trust accrued income and other assets at fair value	13		14		16
Accrued income and other assets	3,004	[1]	3,015	[1]	2,884	[1]
Total assets	90,802		92,934		89,198
Trust accrued expense and other liabilities at fair value	1,297		1,557		1,352
Total liabilities	80,383		82,614		78,819
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans, net of unearned income of ($6), ($6), and ($5)	2,318		2,390		2,599
Less: Allowance for loan and lease losses	34		39		49
Net loans	4,320		4,458		5,037
Accrued income and other assets	41		45		97
Total assets	4,427		4,572		5,182
Total liabilities	1,819		1,854		2,176
Education Lending [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assets	4,380		4,523		5,116
Total liabilities	1,816		1,854		2,151
Education Lending [Member] | Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans, net of unearned income of ($6), ($6), and ($5)	2,318		2,390		2,599
Less: Allowance for loan and lease losses	34		39		49
Net loans	4,320		4,458		5,037
Accrued income and other assets	41		45		54
Trust [Member] | Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	1,893		1,960		2,333
Trust accrued income and other assets at fair value	19		20		25
Trust accrued expense and other liabilities at fair value	20		20		25
Trust securities at fair value	1,796		1,834		2,126
Trust [Member] | Education Lending [Member] | Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	1,893		1,960		2,333
Trust accrued income and other assets at fair value	19		20		25
Trust accrued expense and other liabilities at fair value	20		20		25
Trust securities at fair value	1,796		1,834		2,126
Portfolio [Member] | Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	143		147		154
Portfolio [Member] | Education Lending [Member] | Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	$ 143		$ 147		$ 154

[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.