Acquisitions and Discontinued Operations - Components of Assets and Liabilities of Education Lending Business (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans at fair value	$ 151		$ 157		$ 73
Loans, net of unearned income of ($5), ($5) and ($2)	53,101		52,822		49,605
Less: Allowance for loan and lease losses	876		888		888
Net loans	52,225		51,934		48,717
Accrued income and other assets	2,864	[1]	2,774	[1]	2,967	[1]
Total assets	90,639		89,236		86,523
Trust accrued expense and other liabilities at fair value	1,421		1,387		1,390
Total liabilities	80,378		78,927		76,347
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 ($5), ($5) and ($2)	2,524		2,675		2,830
Less: Allowance for loan and lease losses	41		55		79
Net loans	4,951		5,146		5,404
Accrued income and other assets	87		87		87
Total assets	5,084		5,282		5,545
Total liabilities	2,169		2,220		2,428
Education Lending [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assets	5,027		5,232		5,511
Total liabilities	2,139		2,181		2,401
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 ($5), ($5) and ($2)	2,524		2,675		2,830
Less: Allowance for loan and lease losses	41		55		79
Net loans	4,951		5,146		5,404
Accrued income and other assets	52		60		76
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	2,317		2,369		2,580
Trust accrued income and other assets at fair value	24		26		31
Trust accrued expense and other liabilities at fair value	21		22		28
Trust securities at fair value	2,118		2,159		2,373
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	2,317		2,369		2,580
Trust accrued income and other assets at fair value	24		26		31
Trust accrued expense and other liabilities at fair value	21		22		28
Trust securities at fair value	2,118		2,159		2,373
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	151		157		73
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	$ 151		$ 157		$ 73

[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.