Capital Securities Issued by Unconsolidated Subsidiaries (Details) (USD $)	6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Capital Securities Issued by Unconsolidated Subsidiaries Information
Common Stock	$ 1,017,000,000	$ 946,000,000	$ 946,000,000
Additional Capital Securities Issued By Unconsolidated Subsidiaries (Textuals) [Abstract]
Capital securities issued by the KeyCorp and Union State Bank capital trusts of Tier 1 capital	1,800,000,000
Percentage of Capital securities issued by the KeyCorp and Union State Bank capital trusts of Tier 1 capital	17.00%
Capital securities adjustments related to fair value hedges	121,000,000	6,000,000	4,000,000
Right to redeem debentures	(i) in whole or in part, on or after July 1, 2008 (for debentures owned by KeyCorp Capital I); March 18, 1999 (for debentures owned by KeyCorp Capital II); July 16, 1999 (for debentures owned by KeyCorp Capital III); July 21, 2008 (for debentures owned by KeyCorp Capital V); December 15, 2008 (for debentures owned by KeyCorp Capital VI); June 15, 2011 (for debentures owned by KeyCorp Capital VIII); December 15, 2011 (for debentures owned by KeyCorp Capital IX); March 15, 2013 (for debentures owned by KeyCorp Capital X); February 1, 2007 (for debentures owned by Union State Capital I); July 31, 2006 (for debentures owned by Union State Statutory II); and April 7, 2009 (for debentures owned by Union State Statutory IV); and (ii) in whole at any time within 90 days after and during the continuation of: a “tax event,” a “capital treatment event”, with respect to KeyCorp Capital V, VI, VII, VIII, IX and X only an “investment company event,” and with respect to KeyCorp Capital X only a “rating agency event” (as each is defined in the applicable indenture).
Debentures adjustments related to financial instrument hedging	118,000,000	131,000,000	184,000,000
Redemption price of debentures in the form of Principal amount, if redeemed before maturity	The principal amount, plus any accrued but unpaid interest
Redemption price as the sum of the present values of principal and interest payments, if redeemed before maturity	The greater of (a) the principal amount, plus any accrued but unpaid interest or (b) the sum of the present values of principal and interest payment discounted at the Treasury Rate (as defined in the applicable indenture), plus 20 basis points (25 basis points or 50 basis points in the case of redemption upon either a tax event or a capital treatment event for KeyCorp Capital III), plus any accrued but unpaid interest.
Period of Enactment for Issue of Relevant Regulation for Federal Reserve	18 months
Business Trusts [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	1,912,000,000	1,797,000,000	1,795,000,000
Common Stock	26,000,000	26,000,000	26,000,000
Principal Amount of Debentures, Net of Discount	1,935,000,000	1,948,000,000	2,001,000,000
Interest Rate of Capital Securities and Debentures	6.57%	6.546%	6.546%
KeyCorp Capital I [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	156,000,000
Common Stock	6,000,000
Principal Amount of Debentures, Net of Discount	159,000,000
Interest Rate of Capital Securities and Debentures	1.045%
Maturity of Capital Securities and Debentures	2028
Capital Securities Issued by Unconsolidated Subsidiaries (Textuals) [Abstract]
Floating interest rate	KeyCorp Capital I has a floating interest rate equal to three-month LIBOR plus 74 basis points that reprices quarterly
KeyCorp Capital II [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	98,000,000
Common Stock	4,000,000
Principal Amount of Debentures, Net of Discount	102,000,000
Interest Rate of Capital Securities and Debentures	6.875%
Maturity of Capital Securities and Debentures	2029
KeyCorp Capital III [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	125,000,000
Common Stock	4,000,000
Principal Amount of Debentures, Net of Discount	129,000,000
Interest Rate of Capital Securities and Debentures	7.75%
Maturity of Capital Securities and Debentures	2029
KeyCorp Capital V [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	124,000,000
Common Stock	4,000,000
Principal Amount of Debentures, Net of Discount	128,000,000
Interest Rate of Capital Securities and Debentures	5.875%
Maturity of Capital Securities and Debentures	2033
KeyCorp Capital VI [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	58,000,000
Common Stock	2,000,000
Principal Amount of Debentures, Net of Discount	60,000,000
Interest Rate of Capital Securities and Debentures	6.125%
Maturity of Capital Securities and Debentures	2033
KeyCorp Capital VII [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	191,000,000
Common Stock	5,000,000
Principal Amount of Debentures, Net of Discount	196,000,000
Interest Rate of Capital Securities and Debentures	5.70%
Maturity of Capital Securities and Debentures	2035
KeyCorp Capital VIII [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	173,000,000
Common Stock	0
Principal Amount of Debentures, Net of Discount	173,000,000
Interest Rate of Capital Securities and Debentures	7.00%
Maturity of Capital Securities and Debentures	2066
KeyCorp Capital IX [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	338,000,000
Common Stock	0
Principal Amount of Debentures, Net of Discount	338,000,000
Interest Rate of Capital Securities and Debentures	6.75%
Maturity of Capital Securities and Debentures	2066
KeyCorp Capital X [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	599,000,000
Common Stock	0
Principal Amount of Debentures, Net of Discount	599,000,000
Interest Rate of Capital Securities and Debentures	8.00%
Maturity of Capital Securities and Debentures	2068
Union State Capital I [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	20,000,000
Common Stock	1,000,000
Principal Amount of Debentures, Net of Discount	21,000,000
Interest Rate of Capital Securities and Debentures	9.58%
Maturity of Capital Securities and Debentures	2027
Union State Statutory II [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	20,000,000
Common Stock	0
Principal Amount of Debentures, Net of Discount	20,000,000
Interest Rate of Capital Securities and Debentures	3.853%
Maturity of Capital Securities and Debentures	2031
Capital Securities Issued by Unconsolidated Subsidiaries (Textuals) [Abstract]
Floating interest rate	Three-month LIBOR plus 358 basis points
Union State Statutory IV [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	10,000,000
Common Stock	0
Principal Amount of Debentures, Net of Discount	$ 10,000,000
Interest Rate of Capital Securities and Debentures	3.078%
Maturity of Capital Securities and Debentures	2034
Capital Securities Issued by Unconsolidated Subsidiaries (Textuals) [Abstract]
Floating interest rate	Three-month LIBOR plus 280 basis