Subordinated Debentures Held by Subsidiary Trusts	6 Months Ended
Subordinated Debentures Held by Subsidiary Trusts	Jun. 30, 2012
Subordinated Borrowings [Abstract]
Subordinated Borrowings Disclosure [Text Block]	Subordinated Debentures Held by Subsidiary Trusts On June 26, 2012, the Company redeemed 30-year junior subordinated deferrable interest debentures ("Subordinated Debentures") issued by the Company to First Interstate Statutory Trust I ("FIST"). The redemption price of $41,238 was equal to the $1 liquidation amount of each security plus all accrued and unpaid distributions up to the date of redemption. Unamortized issuance costs of $428 were charged to other expense on the date of redemption. The redemption of the Subordinated Debentures caused a mandatory redemption of $40,000 of 30-year floating rate mandatorily redeemable capital trust preferred securities issued by FIST to third-party investors and $1,238 of common equity securities issued by FIST to the Company.

The entire disclosure for borrowings under subordinated debt agreements that qualify as available in computing net capital under SEC's uniform net capital rule, including restrictive covenants, collateral, interest rates and due dates, amounts due by date and amount owed in total.

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