<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xml:lang="en-US"
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2022"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="cma-20230306.xsd" xlink:type="simple"/>
    <context id="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000028412</identifier>
        </entity>
        <period>
            <startDate>2023-03-06</startDate>
            <endDate>2023-03-06</endDate>
        </period>
    </context>
    <dei:EntityCentralIndexKey
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl80L2ZyYWc6MmVhOWFhNjg0ZDdmNDNlNTg5MDg3NjkzYjdmYWM1ZTUvdGFibGU6MzNiYWYxZTM5MDI2NDM4Y2JjM2IyN2U5ODg4MWRkYTEvdGFibGVyYW5nZTozM2JhZjFlMzkwMjY0MzhjYmMzYjI3ZTk4ODgxZGRhMV80LTEtMS0xLTkzOTU4OA_583a8469-191c-4dcb-9683-c0059e60a9bf">0000028412</dei:EntityCentralIndexKey>
    <dei:AmendmentFlag
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl80L2ZyYWc6MmVhOWFhNjg0ZDdmNDNlNTg5MDg3NjkzYjdmYWM1ZTUvdGFibGU6MzNiYWYxZTM5MDI2NDM4Y2JjM2IyN2U5ODg4MWRkYTEvdGFibGVyYW5nZTozM2JhZjFlMzkwMjY0MzhjYmMzYjI3ZTk4ODgxZGRhMV8xMS0xLTEtMS05Mzk1ODg_d7773ebf-aac5-432c-aa20-02c51a7f9ae3">false</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl85OQ_4d633e98-f427-4554-a3e0-0650a9b5c65d">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8yNDE_b7f1546f-d3e2-4b68-9af3-9760be1677bd">2023-03-06</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8yNDY_58dcb9db-dcb0-4757-ae10-913082d1d34c">COMERICA INCORPORATED</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZjVmMjIzZTY2NjAzNDE2MzgyMThhMmM3YzQ3ODk5ZWMvdGFibGVyYW5nZTpmNWYyMjNlNjY2MDM0MTYzODIxOGEyYzdjNDc4OTllY18wLTAtMS0xLTkzOTU4OA_97d4b4f9-0524-4052-8097-e49cbb24c312">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZjVmMjIzZTY2NjAzNDE2MzgyMThhMmM3YzQ3ODk5ZWMvdGFibGVyYW5nZTpmNWYyMjNlNjY2MDM0MTYzODIxOGEyYzdjNDc4OTllY18wLTEtMS0xLTkzOTU4OA_2d243dc4-5dd5-47e5-b4c2-c6fb3a189236">1-10706</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZjVmMjIzZTY2NjAzNDE2MzgyMThhMmM3YzQ3ODk5ZWMvdGFibGVyYW5nZTpmNWYyMjNlNjY2MDM0MTYzODIxOGEyYzdjNDc4OTllY18wLTItMS0xLTkzOTU4OA_20b55730-4ddf-4f09-b470-c7fc4efeeeb6">38-1998421</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8zMjg_8d345068-3634-4517-bd14-3905f7f44954">1717 Main Street, MC 6404</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8zMzI_ae9800fd-858e-4e6a-9463-4522639fc059">Dallas</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8zMzY_58dfecaf-946f-409a-9ea2-619868539306">TX</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8zNDA_f9b4997d-9af2-44a3-ac89-a6e70873ea6d">75201</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl80Njg_6693a76d-1490-4b74-9e19-3b9318697d1c">(214)</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl80NzE_c5e1580d-b530-4cb0-824a-37537b469bf9">462-6831</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6MmNjOWU2OTY3ZDU0NDY2MWFlOGM1NmI3ZmU5OGQ0ODcvdGFibGVyYW5nZToyY2M5ZTY5NjdkNTQ0NjYxYWU4YzU2YjdmZTk4ZDQ4N18wLTAtMS0xLTkzOTU4OA_0f567887-6f17-4d30-8053-bfed7e33570b">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6MmNjOWU2OTY3ZDU0NDY2MWFlOGM1NmI3ZmU5OGQ0ODcvdGFibGVyYW5nZToyY2M5ZTY5NjdkNTQ0NjYxYWU4YzU2YjdmZTk4ZDQ4N18yLTAtMS0xLTkzOTU4OA_92269725-3c78-4a38-bde1-530ec3df60f4">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6MmNjOWU2OTY3ZDU0NDY2MWFlOGM1NmI3ZmU5OGQ0ODcvdGFibGVyYW5nZToyY2M5ZTY5NjdkNTQ0NjYxYWU4YzU2YjdmZTk4ZDQ4N180LTAtMS0xLTkzOTU4OA_303bb961-934f-44a6-82f6-3808a53bcb26">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6MmNjOWU2OTY3ZDU0NDY2MWFlOGM1NmI3ZmU5OGQ0ODcvdGFibGVyYW5nZToyY2M5ZTY5NjdkNTQ0NjYxYWU4YzU2YjdmZTk4ZDQ4N182LTAtMS0xLTkzOTU4OA_c7f40c1d-4c6f-4b3d-b4a7-4ca98136f7b4">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZjNiNGUxZTZjYzJhNDlhMTkwZGQyNWUyYmZmMzZmNDIvdGFibGVyYW5nZTpmM2I0ZTFlNmNjMmE0OWExOTBkZDI1ZTJiZmYzNmY0Ml8xLTAtMS0xLTkzOTU4OA_b5b7faeb-e5e5-4c79-8995-a40eff47ee02">Common Stock, $5 par value</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZjNiNGUxZTZjYzJhNDlhMTkwZGQyNWUyYmZmMzZmNDIvdGFibGVyYW5nZTpmM2I0ZTFlNmNjMmE0OWExOTBkZDI1ZTJiZmYzNmY0Ml8xLTItMS0xLTkzOTU4OA_77db0d2f-9dd3-4520-84a5-a1e0d6ad65db">CMA</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZjNiNGUxZTZjYzJhNDlhMTkwZGQyNWUyYmZmMzZmNDIvdGFibGVyYW5nZTpmM2I0ZTFlNmNjMmE0OWExOTBkZDI1ZTJiZmYzNmY0Ml8xLTQtMS0xLTkzOTU4OA_0db074f7-f115-421b-a595-d5a19f05122e">NYSE</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGFibGU6ZTE2YzczMDJiZmM3NGQ2NDliMjI4ZjJiZjIwYjA0ZTkvdGFibGVyYW5nZTplMTZjNzMwMmJmYzc0ZDY0OWIyMjhmMmJmMjBiMDRlOV8wLTEtMS0xLTkzOTU4OA_f0e95f4c-2048-4b95-b40e-5f83249ee2bd">false</dei:EntityEmergingGrowthCompany>
    <dei:DocumentPeriodEndDate
      contextRef="ib6967e83a9b04fa2b838b90aea74db4c_D20230306-20230306"
      id="id3VybDovL2RvY3MudjEvZG9jOmJlOGFlYWI1ZGJjNDQ1NGQ5NzBkNWVjMGIzNDc2M2NmL3NlYzpiZThhZWFiNWRiYzQ0NTRkOTcwZDVlYzBiMzQ3NjNjZl8xL2ZyYWc6NGRkMDNlZGRkZjZlNDYyZWJjZTI3NDVkYWJiMTZhMDIvdGV4dHJlZ2lvbjo0ZGQwM2VkZGRmNmU0NjJlYmNlMjc0NWRhYmIxNmEwMl8zMzU1_b7f1546f-d3e2-4b68-9af3-9760be1677bd">2023-03-06</dei:DocumentPeriodEndDate>
</xbrl>
