Capital Securities Issued by Unconsolidated Subsidiaries (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Aug. 31, 2011	Dec. 31, 2010
Capital Securities Issued by Unconsolidated Subsidiaries Information
Common Stock	$ 1,017,000,000		$ 946,000,000
Additional Capital Securities Issued By Unconsolidated Subsidiaries (Textual) [Abstract]
Capital securities issued by the KeyCorp and Union State Bank capital trusts of Tier 1 capital	1,000,000,000
Percentage of Capital securities issued by the KeyCorp and Union State Bank capital trusts of Tier 1 capital	10.40%
Capital securities adjustments related to fair value hedges	160,000,000		6,000,000
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); March 15, 2013 (for debentures owned by KeyCorp Capital X); 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 VII, 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	160,000,000		131,000,000
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
Capital Securities Repurchased		23,000,000
Business Trusts [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	1,206,000,000		1,797,000,000
Common Stock	19,000,000		26,000,000
Principal Amount of Debentures, Net of Discount	1,225,000,000		1,948,000,000
Interest Rate of Capital Securities and Debentures	6.61%		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	162,000,000
Interest Rate of Capital Securities and Debentures	1.112%
Maturity of Capital Securities and Debentures	2028
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Floating interest rate	KeyCorp Capital I has a floating interest rate equal to three-month LIBOR plus 74 basis points that reprices quarterly
Floating interest rate equal to three-month LIBOR plus percentage	0.74%
KeyCorp Capital II [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	114,000,000
Common Stock	4,000,000
Principal Amount of Debentures, Net of Discount	118,000,000
Interest Rate of Capital Securities and Debentures	6.875%
Maturity of Capital Securities and Debentures	2029
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption price greater of sum of the present values of principal and interest payments discounted at the Treasury Rate plus interest rate percentage	0.20%
Redemption price greater of sum of the present values of principal and interest payments discounted at the Treasury Rate plus interest rate percentage in case of tax event	0.25%
Redemption price greater of sum of the present values of principal and interest payments discounted at the Treasury Rate plus interest rate percentage in case of capital treatment event	0.50%
KeyCorp Capital III [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	148,000,000
Common Stock	4,000,000
Principal Amount of Debentures, Net of Discount	152,000,000
Interest Rate of Capital Securities and Debentures	7.75%
Maturity of Capital Securities and Debentures	2029
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption price greater of sum of the present values of principal and interest payments discounted at the Treasury Rate plus interest rate percentage	0.20%
Redemption price greater of sum of the present values of principal and interest payments discounted at the Treasury Rate plus interest rate percentage in case of tax event	0.25%
Redemption price greater of sum of the present values of principal and interest payments discounted at the Treasury Rate plus interest rate percentage in case of capital treatment event	0.50%
KeyCorp Capital V [Member]
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption date of capital securities	Sep. 01, 2011
KeyCorp Capital VI [Member]
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption date of capital securities	Sep. 01, 2011
KeyCorp Capital VII [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	190,000,000
Common Stock	5,000,000
Principal Amount of Debentures, Net of Discount	195,000,000
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 (Textual) [Abstract]
Redemption date of capital securities	Sep. 01, 2011
KeyCorp Capital IX [Member]
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption date of capital securities	Dec. 15, 2011
KeyCorp Capital X [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount	598,000,000
Common Stock	0
Principal Amount of Debentures, Net of Discount	$ 598,000,000
Interest Rate of Capital Securities and Debentures	8.00%
Maturity of Capital Securities and Debentures	2068
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Period of Redemption Rating Agency Event Prior to	Mar. 15, 2013
Period of Redemption Rating Agency Event Within	90 days
Union State Statutory II [Member]
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption date of capital securities	Oct. 31, 2011
Union State Statutory IV [Member]
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption date of capital securities	Oct. 07, 2011
Union State Capital I [Member]
Capital Securities Issued by Unconsolidated Subsidiaries (Textual) [Abstract]
Redemption date of capital securities	Sep. 01, 2011