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Deposits Deposits (Narrative) (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
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Deposits [Abstract] |  |
Domestic certificates of deposit of $250,000 or more | $ 1,400 | $ 1,300
Foreign office time deposits in denominations of $250,000 or more | 32 | 13
Foreign Time Deposits $250,000 or More | $ 32 | $ 13

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

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- References No definition available. + Details
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Data Type: | xbrli:stringItemType
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- Definition Amount of interest-bearing time deposits in foreign banking offices. Time deposits bear interest for a fixed, stated period of time and include certificate of deposits and individual retirement accounts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(12)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 942 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-05(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477314/942-235-S99-1 + Details
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