Legal Proceedings	6 Months Ended
Jun. 30, 2013
Legal Proceedings [Abstract]
Legal Matters and Contingencies [Text Block]	Legal Proceedings On July 13, 2012, Visa and MasterCard each announced a preliminary settlement to resolve the plaintiffs' claims in the multi-district interchange litigation and also announced an agreement in principle to resolve the claims brought against them by certain individual retailers in that same litigation. The proposed settlement includes a cash payment to certain merchants of $6.6 billion, of which Visa is responsible for $4.4 billion, and a provision which would reduce credit card interchange income by 10 basis points over an 8 month period beginning in September 2013. Other provisions include the ability for merchants to surcharge customers for credit card usage, the ability for merchant buying groups to negotiate together with Visa and MasterCard, and the ability to cancel this proposed agreement if more than 25% of all affected merchants opt out of the agreement. The Company estimates that the pre-tax cost of the future reduction of 10 basis points in interchange income for an 8 month period, which is part of the above settlement, would amount to approximately $5.2 million. Accordingly, the Company established a liability in 2012 for these anticipated costs. In December 2011, the Bank reached a class-wide settlement in a class action lawsuit captioned Wolfgeher v. Commerce Bank, Case No. 1:10-cv-22017 (MDL 2036, S.D. Fla.) which alleged that the Bank had improperly charged overdraft fees on certain debit card transactions and claimed refunds for the plaintiff individually and on behalf of other customers as a class. A formal Settlement Agreement and Release related to this lawsuit was signed by the Bank on July 26, 2012. The Bank, while admitting no wrongdoing, agreed to the settlement in order to resolve the litigation and avoid further expense. The settlement provided for a payment of $18.3 million into a class settlement fund, the proceeds of which will be used to issue refunds to class members and to pay attorneys' fees, administrative and other costs, in exchange for a complete release of all claims asserted against the Bank. The Bank also agreed to post debit card transactions in chronological order, which was implemented on February 21, 2013. As a result of the change in the posting order of debit card transactions, the Company currently estimates that overdraft income will be reduced on an annual basis by $3.5 million to $5.5 million. A second suit alleging the same facts and also seeking class-action status was filed on June 4, 2010 in Missouri state court; however, the second suit was resolved by agreement on July 18, 2013, and will be dismissed. On January 4, 2013, the Company was named in a petition by Patrick J. Malloy III, Bankruptcy Trustee for the Bankruptcy Estate of George David Gordon Jr. (“Gordon”). The petition was filed in the District Court in and for Tulsa County, State of Oklahoma and removed to the United States District Court for the Northern District of Oklahoma, and subsequently remanded back to the District Court on May 7, 2013. On May 10, 2013, the Company was served with an amended petition in the case. The amended petition alleges that Gordon was involved in securities fraud and that Bank South, an Oklahoma bank that was subsequently acquired by the Company, together with a lending officer employed by Bank South, are jointly and severally liable, as aiders and abettors of the fraudulent scheme, for losses suffered by defrauded investors. The losses suffered by investors who have assigned their claims to the Trustee are alleged to be in excess of $9 million. The claim alleges that Commerce Bank is liable as a successor by merger to Bank South. Based on facts available to the Company and after discussion with outside counsel handling the matter, it is not possible to determine at this time whether this litigation presents a loss contingency that is probable or estimable. The Company believes it has substantial defenses to this matter and anticipates the matter will be resolved without material loss. No liability has been recorded at this time, in accordance with accounting guidance at ASC 450-20. This matter will continue to be evaluated on an ongoing basis and if further developments result in a loss contingency related to this claim being both probable and estimable, the Company will establish an accrued liability with respect to such loss contingency and record it accordingly. The Company has various other lawsuits pending at June 30, 2013, 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 matters for which it deems a loss is probable and can be reasonably estimated. Some legal matters, which are at early stages in the legal process, have not yet progressed to the point where a loss amount can be estimated.

Legal Proceedings

On July 13, 2012, Visa and MasterCard each announced a preliminary settlement to resolve the plaintiffs' claims in the multi-district interchange litigation and also announced an agreement in principle to resolve the claims brought against them by certain individual retailers in that same litigation. The proposed settlement includes a cash payment to certain merchants of $6.6 billion, of which Visa is responsible for $4.4 billion, and a provision which would reduce credit card interchange income by 10 basis points over an 8 month period beginning in September 2013. Other provisions include the ability for merchants to surcharge customers for credit card usage, the ability for merchant buying groups to negotiate together with Visa and MasterCard, and the ability to cancel this proposed agreement if more than 25% of all affected merchants opt out of the agreement. The Company estimates that the pre-tax cost of the future reduction of 10 basis points in interchange income for an 8 month period, which is part of the above settlement, would amount to approximately $5.2 million. Accordingly, the Company established a liability in 2012 for these anticipated costs.

In December 2011, the Bank reached a class-wide settlement in a class action lawsuit captioned Wolfgeher v. Commerce Bank, Case No. 1:10-cv-22017 (MDL 2036, S.D. Fla.) which alleged that the Bank had improperly charged overdraft fees on certain debit card transactions and claimed refunds for the plaintiff individually and on behalf of other customers as a class. A formal Settlement Agreement and Release related to this lawsuit was signed by the Bank on July 26, 2012. The Bank, while admitting no wrongdoing, agreed to the settlement in order to resolve the litigation and avoid further expense. The settlement provided for a payment of $18.3 million into a class settlement fund, the proceeds of which will be used to issue refunds to class members and to pay attorneys' fees, administrative and other costs, in exchange for a complete release of all claims asserted against the Bank. The Bank also agreed to post debit card transactions in chronological order, which was implemented on February 21, 2013. As a result of the change in the posting order of debit card transactions, the Company currently estimates that overdraft income will be reduced on an annual basis by $3.5 million to $5.5 million. A second suit alleging the same facts and also seeking class-action status was filed on June 4, 2010 in Missouri state court; however, the second suit was resolved by agreement on July 18, 2013, and will be dismissed.

On January 4, 2013, the Company was named in a petition by Patrick J. Malloy III, Bankruptcy Trustee for the Bankruptcy Estate of George David Gordon Jr. (“Gordon”). The petition was filed in the District Court in and for Tulsa County, State of Oklahoma and removed to the United States District Court for the Northern District of Oklahoma, and subsequently remanded back to the District Court on May 7, 2013. On May 10, 2013, the Company was served with an amended petition in the case. The amended petition alleges that Gordon was involved in securities fraud and that Bank South, an Oklahoma bank that was subsequently acquired by the Company, together with a lending officer employed by Bank South, are jointly and severally liable, as aiders and abettors of the fraudulent scheme, for losses suffered by defrauded investors. The losses suffered by investors who have assigned their claims to the Trustee are alleged to be in excess of $9 million. The claim alleges that Commerce Bank is liable as a successor by merger to Bank South. Based on facts available to the Company and after discussion with outside counsel handling the matter, it is not possible to determine at this time whether this litigation presents a loss contingency that is probable or estimable. The Company believes it has substantial defenses to this matter and anticipates the matter will be resolved without material loss. No liability has been recorded at this time, in accordance with accounting guidance at ASC 450-20. This matter will continue to be evaluated on an ongoing basis and if further developments result in a loss contingency related to this claim being both probable and estimable, the Company will establish an accrued liability with respect to such loss contingency and record it accordingly.

The Company has various other lawsuits pending at June 30, 2013, 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 matters for which it deems a loss is probable and can be reasonably estimated. Some legal matters, which are at early stages in the legal process, have not yet progressed to the point where a loss amount can be estimated.