Commitments and Contingencies	9 Months Ended
Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings: First Interstate Bank ("the Bank"), a wholly owned banking subsidiary of the Company, was a defendant in a lender liability lawsuit , Kelly Logging Inc. v. First Interstate Bank ("the case"). The case was tried in August 2014 in the Montana Fourth Judicial District, Missoula County in Missoula, Montana ("the court"). On August, 2014, a jury awarded damages to Kelly Logging of $17,047, which included $287 in compensatory damages and $16,760 in punitive damages. On October 1, 2014, a non-final judgment was entered in this matter in the amount of $17,047 plus reasonable attorney fees and interest. The non-final judgment is subject to the court's mandatory review of the jury's punitive damages award and rulings on pending post-trial motions including the Bank's motions asserting that, among other things, Kelly Logging did not provide legally sufficient evidence to support its claims of damage and requesting a reduction of the jury's punitive damages award. On October 14, 2014, the Company filed with the Montana Supreme Court, a petition for writ of supervisory control vacating the October 1, 2014, judgment entered by the court asserting that the court failed to fulfill its statutory duty before entering judgment, thereby violating the Bank's constitutional rights and on October 16, 2014, the Montana Supreme Court ordered the court to file a summary response to the petition within 10 days. On October 21, 2014, the court entered a revised non-final judgment to clarify that the judgment entered on October 1, 2014 was a conditional judgment that could not be enforced and did not create a judgment lien or trigger the time for appeal. On October 28, 2014, the court responded to the Montana Supreme Court requesting the writ of supervisory control be denied because the issues brought forth were moot. On October 29, 2014, the Company filed a post-trial motion moving the court to alter or amend its October 21, 2014 judgment to reflect judgment in the Company's favor or, alternatively, grant a new trial as to all of the claims to correct manifest errors of law or fact upon which the judgment was based. An evidentiary hearing on Kelly Logging's attorney's fees and costs and oral argument on all post-trial motions has been set by the court for November 12, 2014. The Company intends to continue to defend itself vigorously in this litigation and believes it has valid bases in law and fact to overturn or appeal the verdict. In recent appellate cases, the Montana Supreme Court has reduced excessive punitive damage awards to comply with the upper limit of the federal due process guidelines, or to an amount equal to no more than nine times the compensatory damages awarded, in even the most egregious cases. Although the Company believes it has meritorious defenses and appellate issues for this litigation, these proceedings are subject to many uncertainties and, given their complexity and scope, the final outcome cannot be predicted and could have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company. During third quarter 2014, the Company accrued $4,000 of litigation-related expense, which takes into consideration the federal due process guidelines related to punitive damage awards and estimates of the plaintiff's attorneys fees and interest. This accrual is included in non-core expenses in the accompanying consolidated statement of income. In the normal course of business, the Company is involved in various other claims and litigation. In the opinion of management, following consultation with legal counsel, the ultimate liability or disposition thereof of all other claims and litigation is not expected to have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company. Other Commitments: As of September 30, 2014, the Company had commitments under construction agreements of $365 and commitments to purchase available-for-sale U.S. government agency securities of $9,995.

Commitments and Contingencies

Legal Proceedings:

First Interstate Bank ("the Bank"), a wholly owned banking subsidiary of the Company, was a defendant in a lender liability lawsuit , Kelly Logging Inc. v. First Interstate Bank ("the case"). The case was tried in August 2014 in the Montana Fourth Judicial District, Missoula County in Missoula, Montana ("the court"). On August, 2014, a jury awarded damages to Kelly Logging of $17,047, which included $287 in compensatory damages and $16,760 in punitive damages. On October 1, 2014, a non-final judgment was entered in this matter in the amount of $17,047 plus reasonable attorney fees and interest. The non-final judgment is subject to the court's mandatory review of the jury's punitive damages award and rulings on pending post-trial motions including the Bank's motions asserting that, among other things, Kelly Logging did not provide legally sufficient evidence to support its claims of damage and requesting a reduction of the jury's punitive damages award. On October 14, 2014, the Company filed with the Montana Supreme Court, a petition for writ of supervisory control vacating the October 1, 2014, judgment entered by the court asserting that the court failed to fulfill its statutory duty before entering judgment, thereby violating the Bank's constitutional rights and on October 16, 2014, the Montana Supreme Court ordered the court to file a summary response to the petition within 10 days. On October 21, 2014, the court entered a revised non-final judgment to clarify that the judgment entered on October 1, 2014 was a conditional judgment that could not be enforced and did not create a judgment lien or trigger the time for appeal. On October 28, 2014, the court responded to the Montana Supreme Court requesting the writ of supervisory control be denied because the issues brought forth were moot. On October 29, 2014, the Company filed a post-trial motion moving the court to alter or amend its October 21, 2014 judgment to reflect judgment in the Company's favor or, alternatively, grant a new trial as to all of the claims to correct manifest errors of law or fact upon which the judgment was based. An evidentiary hearing on Kelly Logging's attorney's fees and costs and oral argument on all post-trial motions has been set by the court for November 12, 2014.

The Company intends to continue to defend itself vigorously in this litigation and believes it has valid bases in law and fact to overturn or appeal the verdict. In recent appellate cases, the Montana Supreme Court has reduced excessive punitive damage awards to comply with the upper limit of the federal due process guidelines, or to an amount equal to no more than nine times the compensatory damages awarded, in even the most egregious cases. Although the Company believes it has meritorious defenses and appellate issues for this litigation, these proceedings are subject to many uncertainties and, given their complexity and scope, the final outcome cannot be predicted and could have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company. During third quarter 2014, the Company accrued $4,000 of litigation-related expense, which takes into consideration the federal due process guidelines related to punitive damage awards and estimates of the plaintiff's attorneys fees and interest. This accrual is included in non-core expenses in the accompanying consolidated statement of income.

In the normal course of business, the Company is involved in various other claims and litigation. In the opinion of management, following consultation with legal counsel, the ultimate liability or disposition thereof of all other claims and litigation is not expected to have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company.

Other Commitments:

As of September 30, 2014, the Company had commitments under construction agreements of $365 and commitments to purchase available-for-sale U.S. government agency securities of $9,995.