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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic income per common share	$ 1.07	$ 0.97	$ 1.94	$ 1.88
Diluted income per common share	$ 1.07	$ 0.97	$ 1.93	$ 1.88
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.	$ 139,553	$ 127,789	$ 252,216	$ 247,241
Less income allocated to nonvested restricted stock	1,313	1,128	2,357	2,184
Net income allocated to common stock	$ 138,240	$ 126,661	$ 249,859	$ 245,057
Weighted average common shares outstanding	128,458	130,079	128,750	130,141
Basic income per common share	$ 1.07	$ 0.97	$ 1.94	$ 1.88
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.	$ 139,553	$ 127,789	$ 252,216	$ 247,241
Less income allocated to nonvested restricted stock	1,312	1,128	2,355	2,182
Net income allocated to common stock	$ 138,241	$ 126,661	$ 249,861	$ 245,059
Weighted average common shares outstanding	128,458	130,079	128,750	130,141
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	153	129	148	198
Weighted average diluted common shares outstanding	128,611	130,208	128,898	130,339
Diluted income per common share	$ 1.07	$ 0.97	$ 1.93	$ 1.88