Document and Entity Information Document - shares	6 Months Ended
	Jun. 30, 2022	Aug. 03, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
Document Transition Report	false
Entity File Number	001-36502
Entity Registrant Name	COMMERCE BANCSHARES, INC.
Entity Incorporation, State or Country Code	MO
Entity Tax Identification Number	43-0889454
Entity Address, Address Line One	1000 Walnut
Entity Address, City or Town	Kansas City,
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	64106
City Area Code	816
Local Phone Number	234-2000
Title of 12(b) Security	$5 Par Value Common Stock
Trading Symbol	CBSH
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		119,882,772
Entity Central Index Key	0000022356
Document Fiscal Year Focus	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false