Common Stock (Summary Of Components Used To Calculate Basic And Diluted Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic income per common share	$ 1.03	$ 0.92	$ 1.98	$ 1.84
Diluted income per common share	$ 1.02	$ 0.92	$ 1.97	$ 1.84
Basic income per common share:
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 127,789	$ 115,794	$ 247,241	$ 233,948
Less income allocated to nonvested restricted stock	1,128	1,052	2,184	2,122
Net income allocated to common stock	$ 126,661	$ 114,742	$ 245,057	$ 231,826
Weighted average common shares outstanding	123,885	125,637	123,944	125,987
Basic income per common share	$ 1.03	$ 0.92	$ 1.98	$ 1.84
Diluted income per common share:
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 127,789	$ 115,794	$ 247,241	$ 233,948
Less income allocated to nonvested restricted stock	1,128	1,050	2,182	2,118
Net income allocated to common stock	$ 126,661	$ 114,744	$ 245,059	$ 231,830
Weighted average common shares outstanding	123,885	125,637	123,944	125,987
Net effect of the assumed exercise of stock-based awards - based on the treasury stock method using the average market price for the respective periods	122	279	188	293
Weighted average diluted common shares outstanding	124,007	125,916	124,132	126,280
Diluted income per common share	$ 1.02	$ 0.92	$ 1.97	$ 1.84