Principles Of Consolidation And Presentation	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles Of Consolidation And Presentation	Principles of Consolidation and Presentation The accompanying consolidated financial statements include the accounts of Commerce Bancshares, Inc. and all majority-owned subsidiaries (the Company). Effective January 1, 2026, the consolidated financial statements also include the accounts of FineMark Holdings, Inc. ("FineMark"), which was acquired by the Company as described in Note 2 "Acquisition" below, and is consolidated from the date of acquisition. Most of the Company's operations are conducted by its subsidiary bank, Commerce Bank (the Bank). The consolidated financial statements in this report have not been audited by an independent registered public accounting firm, but in the opinion of management, all adjustments necessary to present fairly the financial position and the results of operations for the interim periods have been made. All such adjustments are of a normal recurring nature. All significant intercompany accounts and transactions have been eliminated. Certain reclassifications were made to 2025 data to conform to current year presentation, and certain balances related to the FineMark Holdings, Inc. acquisition were reclassified to conform to the Company's financial statement presentation. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheets and revenues and expenses for the periods. Actual results could differ significantly from those estimates. Management has evaluated subsequent events for potential recognition or disclosure. The results of operations for the six month period ended June 30, 2026 are not necessarily indicative of results to be attained for the full year or any other interim period. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions to Form 10-Q adopted by the Securities and Exchange Commission. Accordingly, the financial statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Company's most recent Annual Report on Form 10-K, containing the latest audited consolidated financial statements and notes thereto. The Company adopted ASU 2025-08 "Financial Instruments - Credit Losses (Topic 326): Purchased Loans" on January 1, 2026. This new guidance makes significant changes to the accounting for certain acquired seasoned loans subject to the current expected credit loss model (CECL). Under the ASU, the initial allowance for credit losses recorded upon the acquisition of loans in scope is recognized as an adjustment to the amortized cost basis of the loan - similar to the model for purchased credit deteriorated assets. For these loans, the "day-one" credit loss estimate does not impact earnings immediately but is instead amortized over time as an adjustment to interest income. Subsequent changes in the allowance for credit losses are reported in earnings within provision for credit losses. The following significant accounting policies have been updated or added since the Company's 2025 Annual Report on Form 10-K to reflect the adoption of ASU 2025-08. Acquired loans - Purchased Credit Deteriorated Loans acquired in a business combination are recognized on the acquisition date at their estimated fair value based on expected future cash flows discounted at a market-based rate of interest and inclusive of adjustments for credit risk, interest rate risk, liquidity, and other factors. Acquired loans that have experienced more-than-insignificant deterioration in credit quality since origination are classified as purchased credit deteriorated ("PCD") loans. An allowance for credit losses is established for the initial estimate of expected credit losses on PCD loans as of the acquisition date and recorded through a gross-up adjustment to the loan’s amortized cost basis. Acquired loans - Purchased Seasoned Loans Non-PCD loans acquired in a business combination are deemed purchased seasoned loans with an allowance for credit losses established for the initial estimate of expected credit losses as of the acquisition date and recorded through a gross-up adjustment to the loans’ amortized cost basis. See Note 2 “Acquisition” for additional information on loans acquired in a business combination.

The accompanying consolidated financial statements include the accounts of Commerce Bancshares, Inc. and all majority-owned subsidiaries (the Company). Effective January 1, 2026, the consolidated financial statements also include the accounts of FineMark Holdings, Inc. ("FineMark"), which was acquired by the Company as described in Note 2 "Acquisition" below, and is consolidated from the date of acquisition. Most of the Company's operations are conducted by its subsidiary bank, Commerce Bank (the Bank). The consolidated financial statements in this report have not been audited by an independent registered public accounting firm, but in the opinion of management, all adjustments necessary to present fairly the financial position and the results of operations for the interim periods have been made. All such adjustments are of a normal recurring nature. All significant intercompany accounts and transactions have been eliminated. Certain reclassifications were made to 2025 data to conform to current year presentation, and certain balances related to the FineMark Holdings, Inc. acquisition were reclassified to conform to the Company's financial statement presentation. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheets and revenues and expenses for the periods. Actual results could differ significantly from those estimates. Management has evaluated subsequent events for potential recognition or disclosure. The results of operations for the six month period ended June 30, 2026 are not necessarily indicative of results to be attained for the full year or any other interim period.

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions to Form 10-Q adopted by the Securities and Exchange Commission. Accordingly, the financial statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Company's most recent Annual Report on Form 10-K, containing the latest audited consolidated financial statements and notes thereto.

The Company adopted ASU 2025-08 "Financial Instruments - Credit Losses (Topic 326): Purchased Loans" on January 1, 2026. This new guidance makes significant changes to the accounting for certain acquired seasoned loans subject to the current expected credit loss model (CECL). Under the ASU, the initial allowance for credit losses recorded upon the acquisition of loans in scope is recognized as an adjustment to the amortized cost basis of the loan - similar to the model for purchased credit deteriorated assets. For these loans, the "day-one" credit loss estimate does not impact earnings immediately but is instead amortized over time as an adjustment to interest income. Subsequent changes in the allowance for credit losses are reported in earnings within provision for credit losses.

Loans acquired in a business combination are recognized on the acquisition date at their estimated fair value based on expected future cash flows discounted at a market-based rate of interest and inclusive of adjustments for credit risk, interest rate risk, liquidity, and other factors. Acquired loans that have experienced more-than-insignificant deterioration in credit quality since origination are classified as purchased credit deteriorated ("PCD") loans. An allowance for credit losses is established for the initial estimate of expected credit losses on PCD loans as of the acquisition date and recorded through a gross-up adjustment to the loan’s amortized cost basis.

Non-PCD loans acquired in a business combination are deemed purchased seasoned loans with an allowance for credit losses established for the initial estimate of expected credit losses as of the acquisition date and recorded through a gross-up adjustment to the loans’ amortized cost basis. See Note 2 “Acquisition” for additional information on loans acquired in a business combination.