XML 121 R62.htm IDEA: XBRL DOCUMENT
v3.21.1

Asset Quality - Changes in Liability for Credit Losses on Lending Related Commitments (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jan. 01, 2020 | Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019
Off-Balance Sheet, Credit Loss, Liability [Roll Forward] |  |  |  |  |  |  |
Balance at the end of the prior period | $ 68 | $ 197 | $ 68 | $ 68 |  |  |
Liability for credit losses on contingent guarantees at the end of the prior period |  |  |  |  |  | $ 0 | $ 7
Balance at beginning of period | 68 | 178 | 161 | 68 | $ 68 | 197 | 68
Provision (credit) for losses on off balance sheet exposures |  | (19) | 20 |  |  |  |
Balance at end of period |  | 178 | 161 | 197 | 68 |  |
Impact of ASC 326 Adoption |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability [Roll Forward] |  |  |  |  |  |  |
Cumulative effect from changes in accounting principle |  |  |  | 0 | 66 |  |
Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability [Roll Forward] |  |  |  |  |  |  |
Balance at the end of the prior period | 141 | 197 | 141 | 141 |  |  |
Balance at beginning of period | 141 | $ 197 | $ 141 | 141 | 141 | $ 197 | $ 141
Balance at end of period |  |  |  | $ 197 | $ 141 |  |
Other Financial Assets | Impact of ASC 326 Adoption |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability [Roll Forward] |  |  |  |  |  |  |
Cumulative effect from changes in accounting principle | $ 4 |  |  |  |  |  |

X
- Definition Off-Balance Sheet, Credit Loss, Liability, Contingent Guarantees + References No definition available. + Details
Name: | key_OffBalanceSheetCreditLossLiabilityContingentGuarantees
Namespace Prefix: | key_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Off-Balance Sheet, Credit Loss, Liability, Excluding Provision For Other Financial Assets + References No definition available. + Details
Name: | key_OffBalanceSheetCreditLossLiabilityExcludingProvisionForOtherFinancialAssets
Namespace Prefix: | key_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expense (reversal of expense) for expected credit loss on off-balance sheet commitment, from change in methodology. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 11 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919244-210447 + Details
Name: | us-gaap_OffBalanceSheetCreditLossLiabilityChangeInMethodCreditLossExpenseReversal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 + Details
Name: | us-gaap_OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_OffBalanceSheetCreditLossLiabilityRollforward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=key_OtherFinancialAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |