No definition available.

Name:	key_CompliancePeriodOfProperty
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Defaults under loan guarantees.

No definition available.

Name:	key_DefaultsUnderLoanGuarantees
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Data Type:	xbrli:integerItemType
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Period Type:	instant

Expiration of guarantees.

No definition available.

Name:	key_ExpirationOfGuarantees
Namespace Prefix:	key_
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Potential undiscounted future payments maximum limit.

No definition available.

Name:	key_PotentialUndiscountedFuturePaymentsMaximumLimit
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Data Type:	xbrli:stringItemType
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Remaining actual life letters of credit.

No definition available.

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Remaining weighted-average life of standby letters of credit.

No definition available.

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Weighted average life of written put options.

No definition available.

Name:	key_WeightedAverageLifeOfWrittenPutOptions
Namespace Prefix:	key_
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Weighted-average remaining term for outstanding commercial mortgage loans.

No definition available.

Name:	key_WeightedAverageRemainingTermForOutstandingCommercialMortgageLoans
Namespace Prefix:	key_
Data Type:	xbrli:durationItemType
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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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Indicates, if estimable, (as a percentage) the approximate extent to which the proceeds from liquidation of any assets held either as collateral or by third parties would be expected to cover the maximum potential amount of future payments under the guarantee or each group of similar guarantees.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsLiquidationProceedsPercentage
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Data Type:	num:percentItemType
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Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25383-109308

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

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Namespace Prefix:
Data Type:	na
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Namespace Prefix:
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