Acquisition and Discontinued Operations (Details 9) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011		Mar. 31, 2011	Dec. 31, 2010
Combined assets and liabilities of the discontinued operations
Cash and due from banks	$ 717			$ 694			$ 853			$ 278
Loans, net of unearned income of ($2), ($2) and $1	49,605			49,575			47,840
Less: Allowance for loan and lease losses	888			1,004			1,230
Net loans	48,717			48,571			46,610
Loans held for sale	656		511	728		479	381		426
Trust accrued income and other assets at fair value	2,978	[1]		3,077	[1]		2,968	[1]
Total assets	5,533	[1]		5,860	[1]		6,328	[1]
Accrued expense and other liabilities	1,417			1,763			1,518
Total liabilities	2,401	[1]		2,550	[1]		2,950	[1]
Segment, Discontinued Operations [Member]
Combined assets and liabilities of the discontinued operations
Cash and due from banks	22			31			32
Loans, net of unearned income of ($2), ($2) and $1	2,830			3,010			3,161
Less: Allowance for loan and lease losses	79			104			109
Net loans	5,404			5,708			6,152
Accrued income and other assets	76			87			110
Total liabilities	2,401			2,550			2,950
Segment, Discontinued Operations [Member] | Trust [Member]
Combined assets and liabilities of the discontinued operations
Trust loans accounted for at fair value	2,580			2,726			3,100
Trust accrued income and other assets at fair value	31			34			34
Accrued expense and other liabilities	28			28			31
Trust securities at fair value	2,373			2,522			2,919
Segment, Discontinued Operations [Member] | Portfolio [Member]
Combined assets and liabilities of the discontinued operations
Trust loans accounted for at fair value	$ 73			$ 76

[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.