Regulatory Capital Requirements (Schedule Of Capital Amounts And Ratios On Consolidated Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Total Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	10.00%
Tier I Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	8.00%
Tier I Common Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	6.50%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Well-Capitalized Capital Requirement Ratio	5.00%
Commerce Bancshares, Inc. (Consolidated) [Member]
Total Capital (to risk-weighted assets), Actual Amount	$ 4,353,905	$ 4,108,270
Total Capital (to risk-weighted assets), Actual Ratio	18.16%	17.48%
Total Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,917,661	$ 1,880,032
Total Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	8.00%	8.00%
Tier I Capital (to risk-weighted assets), Actual Amount	$ 4,156,776	$ 3,926,446
Tier I Capital (to risk-weighted assets), Actual Ratio	17.34%	16.71%
Tier I Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,438,246	$ 1,410,024
Tier I Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	6.00%	6.00%
Tier I Common Capital (to risk-weighted assets), Actual Amount	$ 4,156,776	$ 3,926,446
Tier I Common Capital (to rIsk-weighted assets), Actual Rato	17.34%	16.71%
Tier I Common Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,078,684	$ 1,057,518
Tier I Common Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	4.50%	4.50%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Actual Amount	$ 4,156,776	$ 3,926,446
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Actual Ratio	12.65%	12.26%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Minimum Capital Requirement Amount	$ 1,314,066	$ 1,281,116
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Minimum Capital Requirement Ratio	4.00%	4.00%
Commerce Bank [Member]
Total Capital (to risk-weighted assets), Actual Amount	$ 3,833,780	$ 3,484,249
Total Capital (to risk-weighted assets), Actual Ratio	16.15%	14.98%
Total Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,899,151	$ 1,861,121
Total Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	8.00%	8.00%
Total Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Amount	$ 2,373,939	$ 2,326,401
Total Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	10.00%	10.00%
Tier I Capital (to risk-weighted assets), Actual Amount	$ 3,636,651	$ 3,302,425
Tier I Capital (to risk-weighted assets), Actual Ratio	15.32%	14.20%
Tier I Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,424,364	$ 1,395,841
Tier I Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	6.00%	6.00%
Tier I Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Amount	$ 1,899,151	$ 1,861,121
Tier I Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	8.00%	8.00%
Tier I Common Capital (to risk-weighted assets), Actual Amount	$ 3,636,651	$ 3,302,425
Tier I Common Capital (to rIsk-weighted assets), Actual Rato	15.32%	14.20%
Tier I Common Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,068,273	$ 1,046,880
Tier I Common Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	4.50%	4.50%
Tier I Common Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Amount	$ 1,543,061	$ 1,512,161
Tier I Common Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	6.50%	6.50%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Actual Amount	$ 3,636,651	$ 3,302,425
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Actual Ratio	11.13%	10.36%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Minimum Capital Requirement Amount	$ 1,307,252	$ 1,274,648
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Minimum Capital Requirement Ratio	4.00%	4.00%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Well-Capitalized Capital Requirement Amount	$ 1,634,065	$ 1,593,310
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Well-Capitalized Capital Requirement Ratio	5.00%	5.00%

Tier One Risk Based Common Capital

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Tier One Risk Based Common Capital Required to be Well Capitalized

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Tier One Risk Based Common Capital Required to be Well Capitalized to Risk Weighted Assets

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Tier One Risk Based Common Capital to RIsk Weighted Assets

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Amount of total capital as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

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