Acquisitions	6 Months Ended
Jun. 30, 2014
Business Combinations [Abstract]
Acquisitions	Acquisitions On February 10, 2014, the Company entered into an agreement and plan of merger to acquire all of the outstanding stock of Mountain West Financial Corp ("Mountain West"), a Montana-based bank holding company that operates one wholly-owned subsidiary bank, Mountain West Bank, NA, with branches located in five of the Company's current market areas in Montana. As of June 30, 2014, Mountain West had total assets of approximately $623,355, net loans of approximately $380,410 and deposits of approximately $519,820. Under the terms of the agreement and plan of merger, each outstanding share of Mountain West common stock will be canceled and converted into the right to receive 0.2552 shares of the Company's Class A common stock plus $7.125 in cash, or, if a Mountain West stockholder properly elects and subject to the limitations contained within the agreement and plan of merger, an amount in all cash or all stock intended to be substantially equal in value to the above described combination of stock and cash merger consideration. The value received by Mountain West stockholders in the aggregate and on a per share of Mountain West common stock basis will fluctuate prior to the completion of the merger based on the prevailing market price of the Company's Class A common stock at the time the transaction is consummated. The merger is expected to be completed after the close of business on July 31, 2014. Subject to regulatory approval, the Company anticipates Mountain West Bank, NA will be merged with and into FIB on October 18, 2014. For additional information regarding the acquisition, see Note 17 - Subsequent Events.

Acquisitions

On February 10, 2014, the Company entered into an agreement and plan of merger to acquire all of the outstanding stock of Mountain West Financial Corp ("Mountain West"), a Montana-based bank holding company that operates one wholly-owned subsidiary bank, Mountain West Bank, NA, with branches located in five of the Company's current market areas in Montana. As of June 30, 2014, Mountain West had total assets of approximately $623,355, net loans of approximately $380,410 and deposits of approximately $519,820.

Under the terms of the agreement and plan of merger, each outstanding share of Mountain West common stock will be canceled and converted into the right to receive 0.2552 shares of the Company's Class A common stock plus $7.125 in cash, or, if a Mountain West stockholder properly elects and subject to the limitations contained within the agreement and plan of merger, an amount in all cash or all stock intended to be substantially equal in value to the above described combination of stock and cash merger consideration. The value received by Mountain West stockholders in the aggregate and on a per share of Mountain West common stock basis will fluctuate prior to the completion of the merger based on the prevailing market price of the Company's Class A common stock at the time the transaction is consummated.

The merger is expected to be completed after the close of business on July 31, 2014. Subject to regulatory approval, the Company anticipates Mountain West Bank, NA will be merged with and into FIB on October 18, 2014. For additional information regarding the acquisition, see Note 17 - Subsequent Events.