Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 205	$ 200
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on securities available for sale, net of income taxes of $(13) and ($6)	(22)	(11)
Net unrealized gains (losses) on derivative financial instruments, net of income taxes of $(5) and $7	(8)	12
Foreign currency translation adjustments, net of income taxes	(11)	6
Net pension and postretirement benefit costs, net of income taxes	3	2
Total other comprehensive income (loss), net of tax	(38)	9
Comprehensive income (loss)	167	209
Less: Comprehensive income attributable to noncontrolling interests	1
Comprehensive income (loss) attributable to Key	$ 166	$ 209