Parent Company Condensed Financial Statements (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments in marketable common and preferred stock	$ 7,153,000	$ 2,966,000
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
Parent line of credit with Bank, borrowings during period	0	$ 0	$ 0
Financial Instruments Owned Corporate Bonds	4,800,000
Investments in marketable common and preferred stock	6,900,000
Equity Securities without Readily Determinable Fair Value, Amount	$ 1,100,000