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v3.19.3.a.u2

Leases - Narrative (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items] |
Amount of extension of lease term | 5 years
Carrying amount of residual assets covered by residual value guarantees | $ 289
Carrying amount of operating lease assets | $ 941
Leases, Excluding Ground Leases [Member] | Minimum [Member] |
Lessee, Lease, Description [Line Items] |
Lessee, lease term of operating or financing leases | 1 year
Leases, Excluding Ground Leases [Member] | Maximum [Member] |
Lessee, Lease, Description [Line Items] |
Lessee, lease term of operating or financing leases | 20 years
Ground Leases [Member] |
Lessee, Lease, Description [Line Items] |
Lessee, lease term of operating or financing leases | 30 years

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- Definition Lessee, Lease, Term Of Contract + References No definition available. + Details
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Namespace Prefix: | key_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Lessee, Operating And Finance Lease, Renewal Term + References No definition available. + Details
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Namespace Prefix: | key_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount lessor expects from underlying asset following end of operating lease term. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=119202524&loc=SL77919359-209981 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of residual asset covered by residual value guarantee. Excludes guarantee considered to be lease payments for lessor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 30 -Section 50 -Paragraph 7 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=119202524&loc=SL77919381-209981 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |