Parent Company Condensed Financial Statements (Condensed Statements Of Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Interest and dividends on investment securities	$ 310,181	$ 271,774	$ 278,755
Salaries and employee benefits	628,453	607,862	584,063
Professional and other services	48,856	35,077	36,198
Data processing fees paid to affiliates	133,970	127,390	118,758
Other	38,296	48,932	41,692
Total non-interest expense	979,826	951,229	930,982
Income tax expense (benefit)	161,136	145,089	134,549
NET INCOME ATTRIBUTABLE TO COMMERCE BANCSHARES, INC.	566,251	526,331	477,060
Commerce Bancshares, Inc. (Parent) [Member]
Dividends received from consolidated subsidiary banks	240,002	215,001	280,000
Earnings of consolidated subsidiaries, net of dividends	338,060	191,421	203,570
Interest and dividends on investment securities	2,084	2,282	2,905
Management fees charged subsidiaries	45,776	42,296	47,773
Investment securities gains (losses)	1,408	176,863	(621)
Net interest income on advances and note to subsidiaries	1,996	2,415	2,636
Other	4,099	3,294	2,842
Total income	633,425	633,572	539,105
Salaries and employee benefits	44,778	44,520	41,549
Professional and other services	3,564	3,495	3,580
Data processing fees paid to affiliates	3,041	3,316	3,347
Community Service	0	5,000	0
Other	19,525	15,390	16,264
Total non-interest expense	70,908	71,721	64,740
Income tax expense (benefit)	(3,734)	35,520	(2,695)
NET INCOME ATTRIBUTABLE TO COMMERCE BANCSHARES, INC.	$ 566,251	$ 526,331	$ 477,060