Legal and Regulatory Proceedings (Notes)	9 Months Ended
Sep. 30, 2016
Legal Proceedings [Abstract]
Legal Matters and Contingencies [Text Block]	Legal and Regulatory Proceedings On August 15, 2014, a customer filed a class action complaint against the Bank in the Circuit Court, Jackson County, Missouri. The case is Cassandra Warren, et al v. Commerce Bank (Case No. 1416-CV19197). In the case, the customer alleges violation of the Missouri usury statute in connection with the Bank charging overdraft fees in connection with point-of-sale/debit and automated-teller machine cards. The class was certified and consists of Missouri customers of the Bank who may have been similarly affected. The case has been stayed pending the final outcome of a similar case in which a ruling has been made in favor of the bank defendant. The Company believes that the stay will remain in effect until any appeals in the similar case have run their course. The Company believes the Warren complaint lacks merit and will defend itself vigorously. The amount of any ultimate exposure cannot be determined with certainty at this time. The Company is in ongoing discussions with the U.S. Department of Labor concerning an investigation involving ERISA regulations related to a managed trust account. Currently, no assurances can be given as to the timing for the resolution of the investigation or its outcome, including any ultimate liability. The Company has various other legal proceedings pending at September 30, 2016, arising in the normal course of business. While some matters pending against the Company specify damages claimed by plaintiffs, others do not seek a specified amount of damages or are at very early stages of the legal process. The Company records a loss accrual for all legal and regulatory matters for which it deems a loss is probable and can be reasonably estimated. Some matters, which are in the early stages, have not yet progressed to the point where a loss amount can be determined to be probable and estimable.

Legal and Regulatory Proceedings

On August 15, 2014, a customer filed a class action complaint against the Bank in the Circuit Court, Jackson County, Missouri. The case is Cassandra Warren, et al v. Commerce Bank (Case No. 1416-CV19197). In the case, the customer alleges violation of the Missouri usury statute in connection with the Bank charging overdraft fees in connection with point-of-sale/debit and automated-teller machine cards. The class was certified and consists of Missouri customers of the Bank who may have been similarly affected. The case has been stayed pending the final outcome of a similar case in which a ruling has been made in favor of the bank defendant. The Company believes that the stay will remain in effect until any appeals in the similar case have run their course. The Company believes the Warren complaint lacks merit and will defend itself vigorously. The amount of any ultimate exposure cannot be determined with certainty at this time.

The Company is in ongoing discussions with the U.S. Department of Labor concerning an investigation involving ERISA regulations related to a managed trust account. Currently, no assurances can be given as to the timing for the resolution of the investigation or its outcome, including any ultimate liability.

The Company has various other legal proceedings pending at September 30, 2016, arising in the normal course of business. While some matters pending against the Company specify damages claimed by plaintiffs, others do not seek a specified amount of damages or are at very early stages of the legal process. The Company records a loss accrual for all legal and regulatory matters for which it deems a loss is probable and can be reasonably estimated. Some matters, which are in the early stages, have not yet progressed to the point where a loss amount can be determined to be probable and estimable.