Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 271	$ 221	$ 680	$ 662
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on securities available for sale, net of income taxes of ($48), ($17), ($135) and ($48)	(81)	(28)	(228)	(81)
Net unrealized gains (losses) on derivative financial instruments, net of income taxes of $6, $12, ($17) and $17	10	20	(29)	28
Foreign currency translation adjustments, net of income taxes	2	9	(12)	5
Net pension and postretirement benefit costs, net of income taxes	18	2	24	7
Total other comprehensive income (loss), net of tax	(51)	3	(245)	(41)
Comprehensive income (loss)	220	224	435	621
Less: Comprehensive income attributable to noncontrolling interests	(1)	2		7
Comprehensive income (loss) attributable to Key	$ 221	$ 222	$ 435	$ 614