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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 68,185	$ 68,224	$ 199,029	$ 195,046
Preferred Stock Dividends	1,800	0	1,800	0
Net Income (Loss) Available to Common Stockholders	66,385	68,224	197,229	195,046
Basic income per common share	$ 0.72	$ 0.71	$ 2.09	$ 2.04
Diluted income per common share	$ 0.72	$ 0.71	$ 2.09	$ 2.03
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.	68,185	68,224	199,029	195,046
Preferred Stock Dividends	1,800	0	1,800	0
Net Income (Loss) Available to Common Stockholders	66,385	68,224	197,229	195,046
Less income allocated to nonvested restricted stockholders	879	808	2,537	2,152
Net income available to common stockholders	65,506	67,416	194,692	192,894
Weighted average common shares outstanding	90,575	94,504	92,944	94,499
Basic income per common share	$ 0.72	$ 0.71	$ 2.09	$ 2.04
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	66,385	68,224	197,229	195,046
Less income allocated to nonvested restricted stockholders	877	806	2,530	2,146
Net income available to common stockholders	$ 65,508	$ 67,418	$ 194,699	$ 192,900
Weighted average common shares outstanding	90,575	94,504	92,944	94,499
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	393	471	399	370
Weighted average diluted common shares outstanding	90,968	94,975	93,343	94,869
Diluted income per common share	$ 0.72	$ 0.71	$ 2.09	$ 2.03