Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2012	Aug. 01, 2012 Account
Basis of Presentation (Textual) [Abstract]
Economic interest in unconsolidated investments in voting rights entities, minimum	20.00%
Economic interest in unconsolidated investments in voting rights entities, maximum	50.00%
Economic interest in unconsolidated investments in voting rights entities, Ownership less than	20.00%
Number of consumer and business accounts acquired		400,000
Value of consumer and business accounts acquired		$ 725

Name:	key_BasisOfPresentationTextualAbstract
Namespace Prefix:	key_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Business acquisition, number of consumer and business accounts acquired.

No definition available.

Name:	key_BusinessAcquisitionNumberOfConsumerAndBusinessAccountsAcquired
Namespace Prefix:	key_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Business acquisition, value of consumer and business accounts acquired.

No definition available.

Name:	key_BusinessAcquisitionValueOfConsumerAndBusinessAccountsAcquired
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Economic interest in unconsolidated investments in voting rights entities, maximum.

No definition available.

Name:	key_EconomicInterestInUnconsolidatedInvestmentsInVotingRightsEntitiesMaximum
Namespace Prefix:	key_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Economic interest in unconsolidated investments in voting rights entities, minimum.

No definition available.

Name:	key_EconomicInterestInUnconsolidatedInvestmentsInVotingRightsEntitiesMinimum
Namespace Prefix:	key_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Economic interest in unconsolidated investments in voting rights entities, Ownership less than.

No definition available.

Name:	key_EconomicInterestInUnconsolidatedInvestmentsInVotingRightsEntitiesOwnershipLessThan
Namespace Prefix:	key_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration