Consolidated Statements of Income (Unaudited) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Consolidated Statements of Income [Abstract]
Net tax effect on loss from discontinued operations	$ (3)	$ (6)

Net tax effect on income (loss) from discontinued operations.

No definition available.

Name:	key_NetTaxEffectOnIncomeLossFromDiscontinuedOperations
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration