Asset Quality (Details 11) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Changes in the liability for credit losses on lending-related commitments
Beginning Balance	$ (45)	$ (69)	$ (45)	$ (73)
Provision (credit) for losses on lending-related commitments	6	(12)	6	(16)
Ending Balance	$ (51)	$ (57)	$ (51)	$ (57)

Financing receivable allowance for credit losses liability.

No definition available.

Name:	key_FinancingReceivableAllowanceForCreditLossesLiability
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration