Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital	$ 852,731
Common Equity Tier 1 Capital to Risk Weighted Assets	11.94%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 321,370
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Total Capital, Actual Amount	$ 924,284	$ 890,029
Total Capital (to risk-weighted assets), Ratio	12.94%	14.13%
Total Capital For Capital Adequacy Purposes, Amount	$ 571,324	$ 503,989
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital, Actual Amount	$ 853,182	$ 817,805
Tier 1 Capital (to risk-weighted assets), Ratio	11.95%	12.98%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 428,493	$ 251,995
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	6.00%	4.00%
Tier 1 Capital, Actual Amount	$ 853,182	$ 817,805
Tier 1 Capital (to average assets), Ratio	10.03%	10.57%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 340,420	$ 309,579
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]
Common Equity Tier 1 Capital	$ 839,127
Common Equity Tier 1 Capital to Risk Weighted Assets	11.76%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy	$ 321,168
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Common Equity Tier One Risk Based Capital Required to be Well Capitalized	$ 463,909
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%
Total Capital, Actual Amount	$ 910,229	$ 860,755
Total Capital (to risk-weighted assets), Ratio	12.75%	13.67%
Total Capital For Capital Adequacy Purposes, Amount	$ 570,965	$ 503,852
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	$ 713,706	$ 629,816
Total Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision	10.00%	10.00%
Tier 1 Capital, Actual Amount	$ 839,127	$ 788,531
Tier 1 Capital (to risk-weighted assets), Ratio	11.76%	12.52%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 428,223	$ 251,926
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	6.00%	4.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	$ 570,965	$ 377,889
Tier 1 Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision, Ratio	8.00%	6.00%
Tier 1 Capital, Actual Amount	$ 839,127	$ 788,531
Tier 1 Capital (to average assets), Ratio	9.89%	9.79%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 339,405	$ 322,029
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	$ 424,256	$ 402,537
Tier 1 Capital (to average assets) To Be Well Capitalized Under Prompt Corrective Provision, Ratio	5.00%	5.00%