Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Total risk-based capital:
Actual Amount	$ 850,614	$ 829,443
Actual Ratio	16.70%	16.80%
Adequately Capitalized Amount	407,804	396,210
Adequately Capitalized Ratio	8.00%	8.00%
Tier 1 risk-based capital:
Actual Amount	765,715	739,246
Actual Ratio	15.00%	14.90%
Adequately Capitalized Amount	203,902	198,105
Adequately Capitalized Ratio	4.00%	4.00%
Leverage capital ratio:
Actual Amount	765,715
Actual Ratio	10.40%	10.10%
Adequately Capitalized Amount	295,843	293,414
Adequately Capitalized Ratio	4.00%	4.00%
FIB
Total risk-based capital:
Actual Amount	740,815	723,955
Actual Ratio	14.60%	14.70%
Adequately Capitalized Amount	406,334	394,038
Adequately Capitalized Ratio	8.00%	8.00%
Well Capitalized Amount	507,917	492,548
Well Capitalized Ratio	10.00%	10.00%
Tier 1 risk-based capital:
Actual Amount	668,143	650,093
Actual Ratio	13.20%	13.20%
Adequately Capitalized Amount	203,167	197,019
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	304,750	295,529
Well Capitalized Ratio	6.00%	6.00%
Leverage capital ratio:
Actual Amount	668,143
Actual Ratio	9.10%	8.90%
Adequately Capitalized Amount	295,201	292,199
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	$ 369,002	$ 365,248
Well Capitalized Ratio	5.00%	5.00%