Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended			12 Months Ended
	Jun. 30, 2012		Jun. 30, 2011	Dec. 31, 2011
Held-to-maturity securities, fair value	$ 4,396		$ 19	$ 2,133
Unearned income on loans	1,155		1,460	1,388
Consolidated guaranteed funds VIEs, for accrued income and other assets	91	[1]
Consolidated education loan securitizations trust VIEs at fair value, Discontinued assets	2,611	[1]
Loan securitization trust VIEs	73
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	$ 2,401	[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	71,496,550		63,147,538	63,962,113
Series A Preferred Stock
Preferred stock, liquidation preference	$ 100		$ 100	$ 100
Preferred stock, shares authorized	7,475,000		7,475,000	7,475,000
Preferred stock, dividend rate	7.75%		7.75%	7.75%
Preferred stock, shares issued, Total	2,904,839		2,904,839	2,904,839

[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.