Regulatory Capital (Tables)

3 Months Ended

Mar. 31, 2014

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 March 31, 2014 and December 31, 2013 are presented in the following tables:

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
March 31, 2014
Total risk-based capital:
Consolidated	$	836,502	16.8	%	$	397,506	8.0	%	NA		NA
FIB	728,681		14.7		395,309		8.0		$	494,136	10.0	%
Tier 1 risk-based capital:
Consolidated	753,154		15.2		198,753		4.0		NA		NA
FIB	657,672		13.3		197,654		4.0		$	296,482	6.0
Leverage capital ratio:
Consolidated	753,154		10.3		293,212		4.0		NA		NA
FIB	657,672		9.0		291,961		4.0		$	364,952	5.0

	Actual				Adequately Capitalized				Well Capitalized
	Amount		Ratio		Amount		Ratio		Amount		Ratio
December 31, 2013
Total risk-based capital:
Consolidated	$	829,443	16.8	%	$	396,210	8.0	%	NA		NA
FIB	723,955		14.7		394,038		8.0		$	492,548	10.0	%
Tier 1 risk-based capital:
Consolidated	739,246		14.9		198,105		4.0		NA		NA
FIB	650,093		13.2		197,019		4.0		$	295,529	6.0
Leverage capital ratio:
Consolidated	739,246		10.1		293,414		4.0		NA		NA
FIB	650,093		8.9		292,199		4.0		$	365,248	5.0