Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital Conservation Buffer	4.6347%
Common Equity Tier 1 Capital	$ 873,217	$ 852,731
Common Equity Tier 1 Capital to Risk Weighted Assets	11.645%	11.94%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 337,439	$ 321,370
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Total Capital, Actual Amount	$ 947,436	$ 924,284
Total Capital (to risk-weighted assets), Ratio	12.6347%	12.94%
Total Capital For Capital Adequacy Purposes, Amount	$ 599,892	$ 571,324
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital, Actual Amount	$ 874,688	$ 853,182
Tier 1 Capital (to risk-weighted assets), Ratio	11.6646%	11.95%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 449,919	$ 428,493
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Tier 1 Capital, Actual Amount	$ 874,688	$ 853,182
Tier 1 Capital (to average assets), Ratio	9.5526%	10.03%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 366,263	$ 340,420
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Banking Subsidiaries [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital Conservation Buffer	4.4756%
Common Equity Tier 1 Capital	$ 862,381	$ 839,127
Common Equity Tier 1 Capital to Risk Weighted Assets	11.5051%	11.76%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 337,304	$ 321,168
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier One Risk Based Capital Required to be Well Capitalized	$ 487,217	$ 463,909
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Total Capital, Actual Amount	$ 935,129	$ 910,229
Total Capital (to risk-weighted assets), Ratio	12.4756%	12.75%
Total Capital For Capital Adequacy Purposes, Amount	$ 599,652	$ 570,965
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	$ 749,565	$ 713,706
Total Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision	10.00%	10.00%
Tier 1 Capital, Actual Amount	$ 862,381	$ 839,127
Tier 1 Capital (to risk-weighted assets), Ratio	11.5051%	11.76%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 449,739	$ 428,223
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	$ 599,652	$ 570,965
Tier 1 Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision, Ratio	8.00%	8.00%
Tier 1 Capital, Actual Amount	$ 862,381	$ 839,127
Tier 1 Capital (to average assets), Ratio	9.4275%	9.89%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 365,902	$ 339,405
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	$ 457,378	$ 424,256
Tier 1 Capital (to average assets) To Be Well Capitalized Under Prompt Corrective Provision, Ratio	5.00%	5.00%