Acquisition, Divestiture and Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Income (Loss) From Discontinued Operations, Net Of Taxes
Net interest income	$ 2,267		$ 2,511		$ 2,380
Net interest income (expense) after provision for loan and lease losses	2,327		1,873		(779)
Noninterest income	1,808		1,954		2,035
Noninterest expense	2,790		3,034		3,554
Income (loss) before income taxes	(70)		(37)		(76)
Income taxes	369		186		(1,035)
Income (loss) from discontinued operations, net of taxes	(44)		(23)		(48)
Discontinued Assets and Liabilities of our Education Lending Business
Loans, net of unearned income of ($2) and $1	49,575		50,107
Less: Allowance for loan and lease losses	1,004		1,604
Net loans	48,571		48,503
Loans held for sale	728		467		443
Trust accrued income and other assets at fair value	3,077	[1]	3,876	[1]
Total assets	5,860	[1]	6,554	[1]
Trust accrued expense and other derivative liabilities at fair value	1,026		1,142
Total liabilities	2,550	[1]	2,998	[1]
Education Lending [Member]
Income (Loss) From Discontinued Operations, Net Of Taxes
Income (loss) before income taxes	(69)		(36)		(67)
Income (loss) from discontinued operations, net of taxes	(43)		(22)		(42)
Discontinued Assets and Liabilities of our Education Lending Business
Total assets	5,829		6,521
Total liabilities	2,550		2,997
Segment, Discontinued Operations [Member]
Income (Loss) From Discontinued Operations, Net Of Taxes
Net interest income	138		157		95
Provision for loan and lease losses	113		79		126
Net interest income (expense) after provision for loan and lease losses	25		78		(31)
Noninterest income	(54)		(61)		49
Noninterest expense	41		54		67
Income taxes	(26)		(14)		(28)
Discontinued Assets and Liabilities of our Education Lending Business
Loans, net of unearned income of ($2) and $1	3,010		3,326
Less: Allowance for loan and lease losses	104		114
Net loans	5,708		6,337
Loans held for sale	0		15
Segment, Discontinued Operations [Member] | Trust [Member]
Discontinued Assets and Liabilities of our Education Lending Business
Trust Loans at fair value	2,726		3,125
Trust accrued income and other assets at fair value	121		169
Trust securities at fair value	2,522		2,966
Segment, Discontinued Operations [Member] | Portfolio [Member]
Discontinued Assets and Liabilities of our Education Lending Business
Trust Loans at fair value	76		0
Segment, Discontinued Operations [Member] | Education Lending [Member]
Income (Loss) From Discontinued Operations, Net Of Taxes
Net interest income	138		157		95
Provision for loan and lease losses	113		79		126
Net interest income (expense) after provision for loan and lease losses	25		78		(31)
Noninterest income	(55)		(66)		23
Noninterest expense	39		48		59
Income taxes	(26)		(14)		(25)
Discontinued Assets and Liabilities of our Education Lending Business
Loans, net of unearned income of ($2) and $1	3,010		3,326
Less: Allowance for loan and lease losses	104		114
Net loans	5,708		6,337
Loans held for sale	0		15
Segment, Discontinued Operations [Member] | Education Lending [Member] | Trust [Member]
Discontinued Assets and Liabilities of our Education Lending Business
Trust Loans at fair value	2,726		3,125
Trust accrued income and other assets at fair value	121		169
Trust accrued expense and other derivative liabilities at fair value	28		31
Trust securities at fair value	2,522		2,966
Segment, Discontinued Operations [Member] | Education Lending [Member] | Portfolio [Member]
Discontinued Assets and Liabilities of our Education Lending Business
Trust Loans at fair value	$ 76		$ 0

[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.