Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011	Sep. 30, 2011
Held-to-maturity securities, fair value	$ 4,212		$ 2,133	$ 1,186
Unearned income on loans	980		1,388	1,413
Consolidated guaranteed funds VIEs, for accrued income and other assets	59	[1]
Consolidated education loan securitizations trust VIEs at fair value, Discontinued assets	2,542	[1]
Loan securitization trust VIEs	71	[1]
Aggregate amount of certificates of deposit	$100,000 or more		$100,000 or more	$100,000 or more
Consolidated education loan securitization trust VIEs at fair value, Discontinued liabilities	$ 2,335	[1]
Preferred stock, par value	$ 1		$ 1	$ 1
Preferred stock, shares authorized	25,000,000		25,000,000	25,000,000
Common shares, par value	$ 1		$ 1	$ 1
Common shares, shares authorized	1,400,000,000		1,400,000,000	1,400,000,000
Common shares, shares issued	1,016,969,905		1,016,969,905	1,016,969,905
Treasury stock, shares	80,775,030		63,962,113	64,161,618
Series A Preferred Stock [Member]
Preferred stock, liquidation preference	$ 100		$ 100	$ 100
Preferred stock, shares authorized	7,475,000		7,475,000	7,475,000
Preferred stock, shares issued	2,904,839		2,904,839	2,904,839
Preferred stock, dividend rate	7.75%		7.75%	7.75%

[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.