Regulatory Capital Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total risk-based capital:
Actual Amount	$ 748,431	$ 800,354
Actual Ratio	15.60%	16.50%
Adequately Capitalized Amount	384,014	387,082
Adequately Capitalized Ratio	8.00%	8.00%
Tier 1 risk-based capital:
Actual Amount	652,929	704,229
Actual Ratio	13.60%	14.60%
Adequately Capitalized Amount	192,007	193,541
Adequately Capitalized Ratio	4.00%	4.00%
Leverage capital ratio:
Tier One Leverage Capital	652,929	704,229
Actual Ratio	8.80%	9.80%
Adequately Capitalized Amount	296,559	286,303
Adequately Capitalized Ratio	4.00%	4.00%
FIB
Total risk-based capital:
Actual Amount	697,695	663,860
Actual Ratio	14.60%	13.80%
Adequately Capitalized Amount	382,245	384,987
Adequately Capitalized Ratio	8.00%	8.00%
Well Capitalized Amount	477,806	481,234
Well Capitalized Ratio	10.00%	10.00%
Tier 1 risk-based capital:
Actual Amount	622,466	588,059
Actual Ratio	13.00%	12.20%
Adequately Capitalized Amount	191,122	192,494
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	286,683	288,740
Well Capitalized Ratio	6.00%	6.00%
Leverage capital ratio:
Tier One Leverage Capital	622,466	588,059
Actual Ratio	8.40%	8.20%
Adequately Capitalized Amount	296,061	285,358
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	$ 370,077	$ 356,698
Well Capitalized Ratio	5.00%	5.00%