Parent Company Condensed Financial Statements (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	May 03, 2024
Investments in marketable common and preferred stock			$ 48,359,000	$ 5,723,000
Equity Securities without Readily Determinable Fair Value, Amount			9,083,000	6,978,000
Visa Class A Shares
Proceeds from Sale of Equity Securities	$ 56,800,000	$ 119,800,000	$ 176,600,000
Visa Class B-2 Shares
Equity Securities without Readily Determinable Fair Value, Amount						$ 0
Equity Securities without Readily Determinable Fair Value, Shares			411,723
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			50,800,000
Financial Instruments Owned Corporate Bonds			5,400,000
Investments in marketable common and preferred stock			5,700,000
Equity Securities without Readily Determinable Fair Value, Amount			$ 7,000,000.0