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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Commerce Bancshares, Inc.	$ 69,893	$ 74,353	$ 135,267	$ 135,408
Preferred Stock Dividends	2,250	2,250	4,500	4,500
Net Income (Loss) Available to Common Stockholders	$ 67,643	$ 72,103	$ 130,767	$ 130,908
Basic income per common share	$ 0.70	$ 0.72	$ 1.35	$ 1.30
Diluted income per common share	$ 0.70	$ 0.72	$ 1.35	$ 1.30
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	$ 67,643	$ 72,103	$ 130,767	$ 130,908
Less income allocated to nonvested restricted stockholders	940	997	1,834	1,793
Net income available to common stockholders	$ 66,703	$ 71,106	$ 128,933	$ 129,115
Weighted average common shares outstanding	95,382	99,099	95,474	99,573
Basic income per common share	$ 0.70	$ 0.72	$ 1.35	$ 1.30
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	$ 67,643	$ 72,103	$ 130,767	$ 130,908
Less income allocated to nonvested restricted stockholders	938	995	1,831	1,789
Net income available to common stockholders	$ 66,705	$ 71,108	$ 128,936	$ 129,119
Weighted average common shares outstanding	95,382	99,099	95,474	99,573
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	249	338	232	327
Weighted average diluted common shares outstanding	95,631	99,437	95,706	99,900
Diluted income per common share	$ 0.70	$ 0.72	$ 1.35	$ 1.30