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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 68,545	$ 64,612	$ 203,812	$ 200,020
Preferred Stock Dividends	2,250	2,250	6,750	6,750
Net Income (Loss) Available to Common Stockholders	$ 66,295	$ 62,362	$ 197,062	$ 193,270
Basic income per common share	$ 0.69	$ 0.63	$ 2.04	$ 1.93
Diluted income per common share	$ 0.68	$ 0.63	$ 2.03	$ 1.93
Basic Income Per Common Share [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Available to Common Stockholders	$ 66,295	$ 62,362	$ 197,062	$ 193,270
Less income allocated to nonvested restricted stockholders	913	884	2,747	2,677
Net income available to common stockholders	$ 65,382	$ 61,478	$ 194,315	$ 190,593
Weighted average common shares outstanding	95,426	96,589	95,458	98,568
Basic income per common share	$ 0.69	$ 0.63	$ 2.04	$ 1.93
Diluted Income Per Common Share [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Available to Common Stockholders, Diluted	$ 66,295	$ 62,362	$ 197,062	$ 193,270
Less income allocated to nonvested restricted stockholders	912	883	2,743	2,672
Net income available to common stockholders	$ 65,383	$ 61,479	$ 194,319	$ 190,598
Weighted average common shares outstanding	95,426	96,589	95,458	98,568
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	243	293	236	315
Weighted average diluted common shares outstanding	95,669	96,882	95,694	98,883
Diluted income per common share	$ 0.68	$ 0.63	$ 2.03	$ 1.93