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
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 64,313	$ 61,017
Basic income per common share	$ 0.67	$ 0.64
Diluted income per common share	$ 0.67	$ 0.63
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.	64,313	61,017
Less income allocated to nonvested restricted stockholders	802	594
Net income available to common stockholders	63,511	60,423
Weighted average common shares outstanding	94,773	94,722
Basic income per common share	$ 0.67	$ 0.64
Diluted 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.	64,313	61,017
Less income allocated to nonvested restricted stockholders	799	593
Net income available to common stockholders	$ 63,514	$ 60,424
Weighted average common shares outstanding	94,773	94,722
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	421	244
Weighted average diluted common shares outstanding	95,194	94,966
Diluted income per common share	$ 0.67	$ 0.63