Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Total risk-based capital:
Actual Amount	$ 898,047	$ 829,443
Actual Ratio	16.30%	16.80%
Adequately Capitalized Amount	439,616	396,210
Adequately Capitalized Ratio	8.00%	8.00%
Tier 1 risk-based capital:
Actual Amount	808,289	739,246
Actual Ratio	14.70%	14.90%
Adequately Capitalized Amount	219,808	198,105
Adequately Capitalized Ratio	4.00%	4.00%
Leverage capital ratio:
Actual Amount	808,289
Actual Ratio	10.40%	10.10%
Adequately Capitalized Amount	310,206	293,414
Adequately Capitalized Ratio	4.00%	4.00%
FIB
Total risk-based capital:
Actual Amount	751,699	723,955
Actual Ratio	14.80%	14.70%
Adequately Capitalized Amount	405,953	394,038
Adequately Capitalized Ratio	8.00%	8.00%
Well Capitalized Amount	507,441	492,548
Well Capitalized Ratio	10.00%	10.00%
Tier 1 risk-based capital:
Actual Amount	679,135	650,093
Actual Ratio	13.40%	13.20%
Adequately Capitalized Amount	202,976	197,019
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	304,465	295,529
Well Capitalized Ratio	6.00%	6.00%
Leverage capital ratio:
Actual Amount	679,135
Actual Ratio	9.00%	8.90%
Adequately Capitalized Amount	302,110	292,199
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	377,638	365,248
Well Capitalized Ratio	5.00%	5.00%
Mountain West Bank
Total risk-based capital:
Actual Amount	63,114
Actual Ratio	15.90%
Adequately Capitalized Amount	31,710
Adequately Capitalized Ratio	8.00%
Well Capitalized Amount	39,637
Well Capitalized Ratio	10.00%
Tier 1 risk-based capital:
Actual Amount	63,114
Actual Ratio	15.90%
Adequately Capitalized Amount	15,855
Adequately Capitalized Ratio	4.00%
Well Capitalized Amount	$ 23,782
Well Capitalized Ratio	6.00%