Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Consolidated Statements of Comprehensive Income [Abstract]
Net income (loss)	$ 200	$ 271
Other comprehensive income (loss):
Net unrealized gains (losses) on securities available for sale, net of income taxes of ($6) and ($12)	(11)	(20)
Net unrealized gains (losses) on derivative financial instruments, net of income taxes of $7 and ($5)	12	(8)
Foreign currency translation adjustments	6	9
Net pension and postretirement benefit costs, net of income taxes	2	1
Other comprehensive income (loss), net of tax:	209	253
Net contribution to (distribution from) noncontrolling interests		15
Total comprehensive income (loss) attributable to Key	$ 209	$ 268