XML 131 R115.htm IDEA: XBRL DOCUMENT
v3.20.4

Employee Benefit Plans (Fair Value Of Pension Plan Assets By Asset Category) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
U.S. government obligations |  | $ 838,059 | $ 851,776
Government-sponsored enterprise obligations |  | 54,485 | 139,277
State and municipal obligations |  | 2,045,099 | 1,267,927
Agency mortgage-backed securities |  | 6,712,085 | 3,937,964
Non-agency mortgage-backed securities |  | 361,074 | 809,782
Asset-backed securities |  | 1,882,243 | 1,233,489
Pension Plans [Member] |  |  |
U.S. government obligations |  | 5,306 | 4,746
Government-sponsored enterprise obligations | [1] | 2,142 | 1,302
State and municipal obligations |  | 9,471 | 8,612
Agency mortgage-backed securities | [2] | 6,984 | 8,892
Non-agency mortgage-backed securities |  | 2,225 | 3,919
Asset-backed securities |  | 6,090 | 5,093
Corporate bonds | [3] | 41,278 | 39,663
Mutual funds | [4] | 5,584 | 6,315
Common stocks | [4] | 24,991 | 22,552
International developed markets | [4] | 1,976 | 4,674
Emerging markets | [4] | 3,568 | 1,788
Total |  | 109,615 | 107,556
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] |  |  |
U.S. government obligations |  | 838,059 | 851,776
Government-sponsored enterprise obligations |  | 0 | 0
State and municipal obligations |  | 0 | 0
Agency mortgage-backed securities |  | 0 | 0
Non-agency mortgage-backed securities |  | 0 | 0
Asset-backed securities |  | 0 | 0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Pension Plans [Member] |  |  |
U.S. government obligations |  | 5,306 | 4,746
Government-sponsored enterprise obligations | [1] | 0 | 0
State and municipal obligations |  | 0 | 0
Agency mortgage-backed securities | [2] | 0 | 0
Non-agency mortgage-backed securities |  | 0 | 0
Asset-backed securities |  | 0 | 0
Corporate bonds | [3] | 0 | 0
Mutual funds | [4] | 5,584 | 6,315
Common stocks | [4] | 24,991 | 22,552
International developed markets | [4] | 1,976 | 4,674
Emerging markets | [4] | 3,568 | 1,788
Total |  | 41,425 | 40,075
Significant Other Observable Inputs (Level 2) [Member] |  |  |
U.S. government obligations |  | 0 | 0
Government-sponsored enterprise obligations |  | 54,485 | 139,277
State and municipal obligations |  | 2,037,131 | 1,258,074
Agency mortgage-backed securities |  | 6,712,085 | 3,937,964
Non-agency mortgage-backed securities |  | 361,074 | 809,782
Asset-backed securities |  | 1,882,243 | 1,233,489
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member] |  |  |
U.S. government obligations |  | 0 | 0
Government-sponsored enterprise obligations | [1] | 2,142 | 1,302
State and municipal obligations |  | 9,471 | 8,612
Agency mortgage-backed securities | [2] | 6,984 | 8,892
Non-agency mortgage-backed securities |  | 2,225 | 3,919
Asset-backed securities |  | 6,090 | 5,093
Corporate bonds | [3] | 41,278 | 39,663
Mutual funds | [4] | 0 | 0
Common stocks | [4] | 0 | 0
International developed markets | [4] | 0 | 0
Emerging markets | [4] | 0 | 0
Total |  | 68,190 | 67,481
Significant Unobservable Inputs (Level 3) [Member] |  |  |
U.S. government obligations |  | 0 | 0
Government-sponsored enterprise obligations |  | 0 | 0
State and municipal obligations |  | 7,968 | 9,853
Agency mortgage-backed securities |  | 0 | 0
Non-agency mortgage-backed securities |  | 0 | 0
Asset-backed securities |  | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member] |  |  |
U.S. government obligations |  | 0 | 0
Government-sponsored enterprise obligations | [1] | 0 | 0
State and municipal obligations |  | 0 | 0
Agency mortgage-backed securities | [2] | 0 | 0
Non-agency mortgage-backed securities |  | 0 | 0
Asset-backed securities |  | 0 | 0
Corporate bonds | [3] | 0 | 0
Mutual funds | [4] | 0 | 0
Common stocks | [4] | 0 | 0
International developed markets | [4] | 0 | 0
Emerging markets | [4] | 0 | 0
Total |  | $ 0 | $ 0
[1] | This category represents bonds (excluding mortgage-backed securities) issued by agencies such as the Government National Mortgage Association, the Federal Home Loan Mortgage Corp and the Federal National Mortgage Association.
[2] | This category represents mortgage-backed securities issued by the agencies mentioned in (a).
[3] | This category represents investment grade bonds issued in the U.S., primarily by domestic issuers, representing diverse industries.
[4] | This category represents investments in individual common stocks and equity funds. These holdings are diversified, largely across the technology services, electronic technology, financial services, healthcare, and consumer non-durables industries.

X
- Definition Common stocks + References No definition available. + Details
Name: | cbsh_Commonstocks
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Corporate bonds + References No definition available. + Details
Name: | cbsh_CorporateBonds
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Emerging Market Securities + References No definition available. + Details
Name: | cbsh_EmergingMarketSecurities
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of pension plan assets. + References No definition available. + Details
Name: | cbsh_FairValuePlanAssets
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in Agency mortgage-backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the agency mortgage-backed security). + References No definition available. + Details
Name: | cbsh_FinancialInstrumentsOwnedAgencyMortgageBackedSecuritiesAtFairValue
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in non-agency mortgage-backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the non-agency mortgage-backed security). + References No definition available. + Details
Name: | cbsh_FinancialInstrumentsOwnedNonAgencyMortgageBackedSecuritiesAtFairValue
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition International Developed Market Securities + References No definition available. + Details
Name: | cbsh_InternationalDevelopedMarketSecurities
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Mutual funds + References No definition available. + Details
Name: | cbsh_Mutualfunds
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Other Asset Backed Securities Disclosure + References No definition available. + Details
Name: | cbsh_OtherAssetBackedSecuritiesDisclosure
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition U S Government Sponsored Enterprises Debt Securities + References No definition available. + Details
Name: | cbsh_USGovernmentSponsoredEnterprisesDebtSecurities
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in fixed income obligations issued by state and local governments and authorities. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
Name: | us-gaap_FinancialInstrumentsOwnedStateAndMunicipalGovernmentObligationsAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
Name: | us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |