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Deposits Deposits (Narrative) (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021
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Deposits [Abstract] |  |
Domestic certificates of deposit of $250,000 or more | $ 478 | $ 627
Foreign office time deposits in denominations of $250,000 or more | $ 51 | $ 50

X
- Definition The aggregate amount of time deposit accounts (including certificates of deposit) in denominations that meet or exceed the FDIC insurance limit at the balance sheet date. + References No definition available. + Details
Name: | cma_DomesticTimeDeposits250000orMore
Namespace Prefix: | cma_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Foreign Time Deposits $250,000 or More + References No definition available. + Details
Name: | cma_ForeignTimeDeposits250000OrMore
Namespace Prefix: | cma_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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