Commitments and Contingencies	6 Months Ended
Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies 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. As of June 30, 2018, the Company had commitments under construction contracts of $3.5 million. On April 25, 2018, the Company entered into a definitive agreement to acquire all of the outstanding stock of Northwest Bancorporation, Inc., the parent company of Inland Northwest Bank (“INB”), a Spokane, Washington based community bank with 20 banking offices across Idaho, Oregon and Washington in an all-stock transaction valued at approximately $159.7 million in aggregate, or $20.69 per share of INB stock. The Company believes the transaction, if completed on the terms contemplated, will complement First Interstate’s footprint and will provide First Interstate with a presence in several high-growth markets, including Spokane, Washington, Portland, Oregon and Coeur d’Alene, Idaho. The transaction has been approved by the boards of directors of both companies and is expected to close in the third quarter with the conversion and integration of INB occurring in the fourth quarter of 2018, subject to customary conditions including, regulatory approval, and INB shareholder approval. Residential mortgage loans sold to investors in the secondary market are sold with varying recourse provisions. Essentially all of the loan sales agreements require the repurchase of a mortgage loan by the seller in situations such as breach of representation, warranty or covenant; untimely document delivery; false or misleading statements; failure to obtain certain certificates or insurance; unmarketability; etc. Certain loan sales agreements contain repurchase requirements based on payment-related defects that are defined in terms of the number of days or months since the purchase, the sequence number of the payment, and/or the number of days of payment delinquency. Based on the specific terms stated in the agreements, the Company had $0.6 million of sold residential mortgage loans with recourse provisions still in effect as of June 30, 2018.

Commitments and Contingencies

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.

As of June 30, 2018, the Company had commitments under construction contracts of $3.5 million.

On April 25, 2018, the Company entered into a definitive agreement to acquire all of the outstanding stock of Northwest Bancorporation, Inc., the parent company of Inland Northwest Bank (“INB”), a Spokane, Washington based community bank with 20 banking offices across Idaho, Oregon and Washington in an all-stock transaction valued at approximately $159.7 million in aggregate, or $20.69 per share of INB stock. The Company believes the transaction, if completed on the terms contemplated, will complement First Interstate’s footprint and will provide First Interstate with a presence in several high-growth markets, including Spokane, Washington, Portland, Oregon and Coeur d’Alene, Idaho. The transaction has been approved by the boards of directors of both companies and is expected to close in the third quarter with the conversion and integration of INB occurring in the fourth quarter of 2018, subject to customary conditions including, regulatory approval, and INB shareholder approval.

Residential mortgage loans sold to investors in the secondary market are sold with varying recourse provisions. Essentially all of the loan sales agreements require the repurchase of a mortgage loan by the seller in situations such as breach of representation, warranty or covenant; untimely document delivery; false or misleading statements; failure to obtain certain certificates or insurance; unmarketability; etc. Certain loan sales agreements contain repurchase requirements based on payment-related defects that are defined in terms of the number of days or months since the purchase, the sequence number of the payment, and/or the number of days of payment delinquency. Based on the specific terms stated in the agreements, the Company had $0.6 million of sold residential mortgage loans with recourse provisions still in effect as of June 30, 2018.