Regulatory Capital Requirements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	$ 652,704	$ 636,559
Total Capital (to risk-weighted assets), Ratio	20.62%	21.05%
Total Capital For Capital Adequacy Purposes, Amount	253,242	241,955
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital, Actual Amount	612,584	598,485
Tier 1 Capital (to risk-weighted assets), Ratio	19.35%	19.79%
Tier 1 Capital For Capital Adequacy Purposes, Amount	126,621	120,978
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Capital, Actual Amount	612,584	598,485
Tier 1 Capital (to average assets), Ratio	12.78%	12.96%
Tier 1 Capital For Capital Adequacy Purposes, Amount	191,778	184,780
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	565,677	561,216
Total Capital (to risk-weighted assets), Ratio	17.87%	18.55%
Total Capital For Capital Adequacy Purposes, Amount	253,244	242,028
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Total Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	316,556	302,535
Total Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision	10.00%	10.00%
Tier 1 Capital, Actual Amount	525,556	523,131
Tier 1 Capital (to risk-weighted assets), Ratio	16.60%	17.29%
Tier 1 Capital For Capital Adequacy Purposes, Amount	126,622	121,014
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	189,933	181,521
Tier 1 Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision, Ratio	6.00%	6.00%
Tier 1 Capital, Actual Amount	525,556	523,131
Tier 1 Capital (to average assets), Ratio	11.07%	11.45%
Tier 1 Capital For Capital Adequacy Purposes, Amount	189,986	182,747
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Provision, Amount	$ 237,483	$ 228,434
Tier 1 Capital (to average assets) To Be Well Capitalized Under Prompt Corrective Provision, Ratio	5.00%	5.00%