Parent Company Condensed Financial Statements (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Equity	$ 4,409	$ 50,591
Other assets	382,194	401,074
Total assets	25,463,842	24,833,415
Other liabilities	237,943	180,889
Total liabilities	22,526,693	22,115,231
Stockholders’ equity	2,931,298	2,716,560
Total liabilities and equity	25,463,842	24,833,415
Commerce Bancshares, Inc. (Parent) [Member]
Investment in consolidated subsidiary, Banks	2,587,489	2,409,098
Investment in consolidated subsidiaries, Non-banks	67,538	52,479
Cash	207,462	151,607
Available for sale securities	2,576	4,595
Equity	3,191	49,345
Note receivable due from bank subsidiary	50,000	50,000
Advances to subsidiaries, net of borrowings	19,867	14,571
Income tax benefits	8,590	8,279
Other assets	23,734	19,951
Total assets	2,970,447	2,759,925
Pension obligation	12,645	12,407
Other liabilities	26,504	30,958
Total liabilities	39,149	43,365
Stockholders’ equity	2,931,298	2,716,560
Total liabilities and equity	$ 2,970,447	$ 2,759,925