Regulatory Capital (Tables)

6 Months Ended

Jun. 30, 2012

Banking and Thrift [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations

Actual capital amounts and ratios and selected minimum regulatory thresholds for the Company and its bank subsidiary, First Interstate Bank (“FIB”), as of June 30, 2012 and December 31, 2011 are presented in the following table:

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
June 30, 2012
Total risk-based capital:
Consolidated	$	778,980	16.2	%	$	384,573	8.0	%	NA		NA
FIB	677,619		14.2		382,724		8.0		$	478,406	10.0	%
Tier 1 risk-based capital:
Consolidated	683,363		14.2		192,286		4.0		NA		NA
FIB	602,288		12.6		191,362		4.0		$	287,043	6.0
Leverage capital ratio:
Consolidated	683,363		9.5		286,505		4.0		NA		NA
FIB	602,288		8.4		285,417		4.0		$	356,771	5.0

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
December 31, 2011
Total risk-based capital:
Consolidated	$	800,354	16.5	%	$	387,082	8.0	%	NA		NA
FIB	663,860		13.8		384,987		8.0		$	481,234	10.0	%
Tier 1 risk-based capital:
Consolidated	704,229		14.6		193,541		4.0		NA		NA
FIB	588,059		12.2		192,494		4.0		$	288,740	6.0
Leverage capital ratio:
Consolidated	704,229		9.8		286,303		4.0		NA		NA
FIB	588,059		8.2		285,358		4.0		$	356,698	5.0