Regulatory Capital Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Total risk-based capital:
Actual Amount	$ 829,443	$ 748,431
Actual Ratio	16.80%	15.60%
Adequately Capitalized Amount	396,210	384,014
Adequately Capitalized Ratio	8.00%	8.00%
Tier 1 risk-based capital:
Actual Amount	739,246	652,929
Actual Ratio	14.90%	13.60%
Adequately Capitalized Amount	198,105	192,007
Adequately Capitalized Ratio	4.00%	4.00%
Leverage capital ratio:
Tier One Leverage Capital	739,246	652,929
Actual Ratio	10.10%	8.80%
Adequately Capitalized Amount	293,414	296,559
Adequately Capitalized Ratio	4.00%	4.00%
FIB
Total risk-based capital:
Actual Amount	723,955	697,695
Actual Ratio	14.70%	14.60%
Adequately Capitalized Amount	394,038	382,245
Adequately Capitalized Ratio	8.00%	8.00%
Well Capitalized Amount	492,548	477,806
Well Capitalized Ratio	10.00%	10.00%
Tier 1 risk-based capital:
Actual Amount	650,093	622,466
Actual Ratio	13.20%	13.00%
Adequately Capitalized Amount	197,019	191,122
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	295,529	286,683
Well Capitalized Ratio	6.00%	6.00%
Leverage capital ratio:
Tier One Leverage Capital	650,093	622,466
Actual Ratio	8.90%	8.40%
Adequately Capitalized Amount	292,199	296,061
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	$ 365,248	$ 370,077
Well Capitalized Ratio	5.00%	5.00%