Parent Company Condensed Financial Statements (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	May 03, 2024
Investments in marketable common and preferred stock			$ 47,551,000	$ 48,359,000
Equity Securities without Readily Determinable Fair Value, Amount			$ 9,803,000	9,083,000	$ 6,978,000
Visa Class B-2 Shares
Equity Securities without Readily Determinable Fair Value, Amount						$ 0
Equity Securities without Readily Determinable Fair Value, Shares			411,723
Visa Class A Shares
Proceeds from Sale of Equity Securities	$ 56,800,000	$ 119,800,000		176,600,000
Commerce Bancshares, Inc. (Parent) [Member]
Note receivable due from bank subsidiary			$ 50,000,000	50,000,000
Parent's line of credit facility with the Bank, maximum borrowing capacity			20,000,000.0
Parent line of credit with Bank, borrowings during period			0	$ 0	$ 0
Private Equity Investments, planned additional investments			44,700,000
Financial Instruments Owned Corporate Bonds			941,000
Investments in marketable common and preferred stock			4,600,000
Equity Securities without Readily Determinable Fair Value, Amount			7,700,000
Commerce Bancshares, Inc. (Parent) [Member] | FineMark Holdings, Inc. Common Stock
Investments in marketable common and preferred stock			$ 4,600,000