Common Stock (Summary Of Components Used To Calculate Basic And Diluted Income Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 66,531	$ 65,805	$ 130,844	$ 126,822
Preferred Stock Dividends, Income Statement Impact	0	0	0	0
Net Income (Loss) Available to Common Stockholders, Basic	66,531	65,805	130,844	126,822
Basic income per common share	$ 0.70	$ 0.69	$ 1.37	$ 1.33
Diluted income per common share	$ 0.70	$ 0.69	$ 1.37	$ 1.32
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.	66,531	65,805	130,844	126,822
Preferred Stock Dividends, Income Statement Impact	0	0	0	0
Net Income (Loss) Available to Common Stockholders, Basic	66,531	65,805	130,844	126,822
Less income allocated to nonvested restricted stockholders	856	750	1,658	1,344
Net income available to common stockholders	65,675	65,055	129,186	125,478
Weighted average common shares outstanding	93,529	94,273	94,148	94,496
Basic income per common share	$ 0.70	$ 0.69	$ 1.37	$ 1.33
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	66,531	65,805	130,844	126,822
Less income allocated to nonvested restricted stockholders	854	747	1,653	1,340
Net income available to common stockholders	$ 65,677	$ 65,058	$ 129,191	$ 125,482
Weighted average common shares outstanding	93,529	94,273	94,148	94,496
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	384	394	402	320
Weighted average diluted common shares outstanding	93,913	94,667	94,550	94,816
Diluted income per common share	$ 0.70	$ 0.69	$ 1.37	$ 1.32