Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 235	$ 242
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on securities available for sale, net of income taxes of $33 and $17	55	29
Net unrealized gains (losses) on derivative financial instruments, net of income taxes of $19 and ($1)	32	(1)
Foreign currency translation adjustments, net of income taxes of ($8) and ($4)	(13)	(2)
Net pension and postretirement benefit costs, net of income taxes of $1 and $2	3	2
Net current-period other comprehensive income, net of income taxes	77	28
Comprehensive income (loss)	312	270
Less: Comprehensive income attributable to noncontrolling interests	2
Comprehensive income (loss) attributable to Key	$ 310	$ 270