Regulatory Capital Requirements (Schedule Of Capital Amounts And Ratios On Consolidated Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
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	$ 3,022,023	$ 2,747,863
Total Capital (to risk-weighted assets), Actual Ratio	15.82%	14.35%
Total Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,528,317	$ 1,531,996
Total Capital (to risk-weighted assets), Minimum Capital Requirement Ratio	8.00%	8.00%
Tier I Capital (to risk-weighted assets), Actual Amount	$ 2,861,016	$ 2,567,264
Tier I Capital (to risk-weighted assets), Actual Ratio	14.98%	13.41%
Tier I Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,146,238	$ 1,148,997
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	$ 2,716,232	$ 2,422,480
Tier I Common Capital (to rIsk-weighted assets), Actual Rato	14.22%	12.65%
Tier I Common Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 859,678	$ 861,748
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	$ 2,861,016	$ 2,567,264
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Actual Ratio	11.52%	10.39%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Minimum Capital Requirement Amount	$ 993,564	$ 988,653
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	$ 2,655,591	$ 2,428,789
Total Capital (to risk-weighted assets), Actual Ratio	13.98%	12.76%
Total Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,519,169	$ 1,522,361
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	$ 1,898,962	$ 1,902,951
Total Capital (to risk-weighted assets), Well-Capitalized Capital Requirement Ratio	10.00%	10.00%
Tier I Capital (to risk-weighted assets), Actual Amount	$ 2,494,584	$ 2,268,131
Tier I Capital (to risk-weighted assets), Actual Ratio	13.14%	11.92%
Tier I Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 1,139,377	$ 1,141,771
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	$ 1,519,169	$ 1,522,361
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	$ 2,494,584	$ 2,268,131
Tier I Common Capital (to rIsk-weighted assets), Actual Rato	13.14%	11.92%
Tier I Common Capital (to risk-weighted assets), Minimum Capital Requirement Amount	$ 854,533	$ 856,328
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	$ 1,234,325	$ 1,236,918
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	$ 2,494,584	$ 2,268,131
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Actual Ratio	10.07%	9.20%
Tier I Capital (to adjusted quarterly average assets) (Leverage Ratio), Minimum Capital Requirement Amount	$ 991,185	$ 986,240
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	$ 1,238,981	$ 1,232,800
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 to RIsk Weighted Assets

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Tier 1 Risk Based Capital as defined in the regulations.

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