Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2012
LIHTC funds [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIE	$ 91
Variable Interest Entity, Carrying Amount of Liabilities, Consolidated VIE	84
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIE	119
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIE
Education Loan Securitization Trusts [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIE	2,611
Variable Interest Entity, Carrying Amount of Liabilities, Consolidated VIE	2,401
LIHTC investments [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIE	1,012
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIE
Maximum Exposure To Loss, Unconsolidated VIE	$ 494

Maximum exposure to loss unconsolidated vie.

No definition available.

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

- Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=7880789&loc=d3e5710-111685

+ Details

Name:	us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

+ Details

Name:	us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=7880789&loc=d3e5728-111685

+ Details

Name:	us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

+ Details

Name:	us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant