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
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 65,374	$ 61,055
Preferred Stock Dividends	2,250	2,250
Net Income (Loss) Available to Common Stockholders	$ 63,124	$ 58,805
Basic income per common share	$ 0.65	$ 0.58
Diluted income per common share	$ 0.65	$ 0.58
Basic Income Per Common Share [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 65,374	$ 61,055
Preferred Stock Dividends	2,250	2,250
Net Income (Loss) Available to Common Stockholders	63,124	58,805
Less income allocated to nonvested restricted stockholders	894	796
Net income available to common stockholders	$ 62,230	$ 58,009
Weighted average common shares outstanding	95,566	100,053
Basic income per common share	$ 0.65	$ 0.58
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	$ 63,124	$ 58,805
Less income allocated to nonvested restricted stockholders	893	794
Net income available to common stockholders	$ 62,231	$ 58,011
Weighted average common shares outstanding	95,566	100,053
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	216	314
Weighted average diluted common shares outstanding	95,782	100,367
Diluted income per common share	$ 0.65	$ 0.58