Capital Securities Issued by Unconsolidated Subsidiaries (Details) (USD $)	3 Months Ended						3 Months Ended					3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Mar. 31, 2012 Business Trusts [Member]	Dec. 31, 2011 Business Trusts [Member]	Mar. 31, 2011 Business Trusts [Member]	Mar. 31, 2012 KeyCorp Capital I [Member]	Mar. 31, 2012 KeyCorp Capital II [Member]	Mar. 31, 2012 KeyCorp Capital III [Member]	Apr. 16, 2012 KeyCorp Capital VII [Member]	Mar. 31, 2012 KeyCorp Capital VII [Member]	Mar. 31, 2012 KeyCorp Capital X [Member]
Capital Securities Issued by Unconsolidated Subsidiaries Information
Capital Securities, Net of Discount				$ 1,190,000,000	$ 1,206,000,000	$ 1,890,000,000	$ 156,000,000	$ 109,000,000	$ 141,000,000		$ 190,000,000	$ 594,000,000
Common Stock	1,017,000,000	1,017,000,000	1,017,000,000	19,000,000	19,000,000	26,000,000	6,000,000	4,000,000	4,000,000		5,000,000
Principal Amount of Debentures, Net of Discount				1,209,000,000	1,225,000,000	1,916,000,000	162,000,000	113,000,000	145,000,000		195,000,000	594,000,000
Interest Rate of Capital Securities and Debentures				6.625%	6.61%	6.548%	1.321%	6.875%	7.75%		5.70%	8.00%
Maturity of Capital Securities and Debentures							2028	2029	2029		2035	2068
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
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%	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%	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%	0.50%
Floating interest rate equal to three-month LIBOR plus percentage							0.74%
Period of Redemption Rating Agency Event Prior to												Mar. 15, 2013
Period of Redemption Rating Agency Event Within												90 days
Consent solicitation expiry date										Apr. 27, 2012
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	10.23%
Capital securities adjustments related to fair value hedges	144,000,000	160,000,000	99,000,000
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	$ 144,000,000	$ 160,000,000	$ 99,000,000
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.