Parent Company Condensed Financial Statements (Condensed Statements Of Cash Flows) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
OPERATING ACTIVITIES:
Net income		$ 500,020	$ 540,590	$ 353,885
Other changes, net		15,250	(10,486)	(68,062)
Net cash provided by (used in) operating activities		559,385	597,722	623,992
INVESTING ACTIVITIES
Proceeds from maturities/pay downs of available for sale securities	[1]	2,691,260	3,459,106	2,673,510
Purchases of investment securities	[1]	(2,147,862)	(5,947,891)	(6,991,460)
Purchases of land, buildings and equipment		(65,191)	(56,716)	(33,134)
Net cash provided by (used in) investing activities		242,271	(2,082,758)	(5,390,504)
FINANCING ACTIVITIES
Payments for Repurchase of Redeemable Preferred Stock		0	0	(150,000)
Purchases of treasury stock		(186,622)	(129,361)	(54,163)
Cash dividends paid on common stock		(127,466)	(122,693)	(120,818)
Cash dividends paid on preferred stock		0	0	(6,750)
Net cash provided by (used in) financing activities		(4,200,809)	3,573,662	6,067,032
Increase (decrease) in cash and cash equivalents		(3,399,153)	2,088,626	1,300,520
Income tax payments (receipts), net		116,995	119,665	90,066
Commerce Bancshares, Inc. (Parent) [Member]
OPERATING ACTIVITIES:
Net income		488,399	530,765	354,057
Earnings of consolidated subsidiaries, net of dividends		(203,965)	(200,461)	(148,435)
Other changes, net		2,557	8,842	5,504
Net cash provided by (used in) operating activities		286,991	339,146	211,126
INVESTING ACTIVITIES
(Increase) decrease in investment in subsidiaries, net		(9)	6	3
Proceeds from maturities/pay downs of available for sale securities		38	22	1,410
Purchases of investment securities		(4,534)	(4,786)	(4,863)
(Increase) decrease in advances to subsidiaries, net		19,996	(8,618)	(5,810)
Purchases of land, buildings and equipment		(741)	(28)	(94)
Net cash provided by (used in) investing activities		14,750	(13,404)	(9,354)
FINANCING ACTIVITIES
Payments for Repurchase of Redeemable Preferred Stock		0	0	(150,000)
Purchases of treasury stock		(186,622)	(129,361)	(54,163)
Issuance of stock under equity compensation plans		(8)	(15)	(11)
Cash dividends paid on common stock		(127,466)	(122,693)	(120,818)
Cash dividends paid on preferred stock		0	0	(6,750)
Net cash provided by (used in) financing activities		(314,096)	(252,069)	(331,742)
Increase (decrease) in cash and cash equivalents		(12,355)	73,673	(129,970)
Cash and cash equivalents at beginning of year		245,616	171,943	301,913
Cash and cash equivalents at end of year		233,261	245,616	171,943
Income tax payments (receipts), net		$ (587)	$ (4,808)	$ (3,663)

[1] Available for sale debt securities, equity securities, and other securities.