Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital Conservation Buffer	6.21%
Common Equity Tier One Capital	$ 1,710,981	$ 1,390,958
Common Equity Tier 1 Capital to Risk Weighted Assets	13.01%	12.88%
Common Equity Tier One Capital Required for Capital Adequacy	$ 591,585	$ 486,080
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier One Capital Required for Capital Adequacy - minimum required plus fully phased in capital conservation buffer	$ 920,244	$ 756,125
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets plus capital conservation buffer fully phased-in	7.00%	7.00%
Tier 1 Capital, Actual Amount	$ 1,710,981	$ 1,390,958
Tier 1 Capital (to risk-weighted assets), Ratio	0.1301	0.1288
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 788,780	$ 648,107
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	0.0600	0.0600
Tier One Risk Based Capital Required for Capital Adequacy plus capital conservation buffer fully phased-in	$ 1,117,439	$ 918,152
Tier One Based Capital Required for Capital Adequacy to Risk Weighted Assets plus capital conservation buffer fully phased-in	8.50%	8.50%
Total Capital, Actual Amount	$ 1,868,192	$ 1,561,020
Total Capital (to risk-weighted assets), Ratio	0.1421	0.1445
Total Capital For Capital Adequacy Purposes, Amount	$ 1,051,707	$ 864,143
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	0.0800	0.0800
Capital Required for Capital Adequacy plus capital conservation buffer fully phased-in	$ 1,380,366	$ 1,134,187
Capital Required for Capital Adequacy to Risk Weighted Assets plus capital conservation buffer fully phased-in	10.50%	10.50%
Tier 1 Capital, Actual Amount	$ 1,710,981	$ 1,390,958
Tier 1 Capital (to average assets), Ratio	0.0855	0.0886
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 800,615	$ 628,112
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	0.0400	0.0400
Banking Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital Conservation Buffer	6.18%
Common Equity Tier One Capital	$ 1,716,186	$ 1,411,834
Common Equity Tier 1 Capital to Risk Weighted Assets	13.06%	13.08%
Common Equity Tier One Capital Required for Capital Adequacy	$ 591,154	$ 485,775
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier One Capital Required for Capital Adequacy - minimum required plus fully phased in capital conservation buffer	$ 919,754	$ 755,651
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets plus capital conservation buffer fully phased-in	7.00%	7.00%
Common Equity Tier One Risk Based Capital Required to be Well Capitalized	$ 853,890	$ 701,676
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital, Actual Amount	$ 1,716,186	$ 1,411,834
Tier 1 Capital (to risk-weighted assets), Ratio	0.1306	0.1308
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 788,206	$ 647,700
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	0.0600	0.0600
Tier One Risk Based Capital Required for Capital Adequacy plus capital conservation buffer fully phased-in	$ 1,116,625	$ 917,576
Tier One Based Capital Required for Capital Adequacy to Risk Weighted Assets plus capital conservation buffer fully phased-in	8.50%	8.50%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	$ 1,050,941	$ 863,601
Tier 1 Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision, Ratio	0.0800	0.0800
Total Capital, Actual Amount	$ 1,863,397	$ 1,546,804
Total Capital (to risk-weighted assets), Ratio	0.1418	0.1433
Total Capital For Capital Adequacy Purposes, Amount	$ 1,050,941	$ 863,601
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	0.0800	0.0800
Capital Required for Capital Adequacy plus capital conservation buffer fully phased-in	$ 1,379,360	$ 1,133,476
Capital Required for Capital Adequacy to Risk Weighted Assets plus capital conservation buffer fully phased-in	10.50%	10.50%
Total Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	$ 1,313,677	$ 1,079,501
Total Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision	0.1000	0.1000
Tier 1 Capital, Actual Amount	$ 1,716,186	$ 1,411,834
Tier 1 Capital (to average assets), Ratio	0.0860	0.0908
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 798,206	$ 622,171
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	0.0400	0.0400
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Provision, Amount	$ 997,757	$ 777,714
Tier 1 Capital (to average assets) To Be Well Capitalized Under Prompt Corrective Provision, Ratio	0.0500	0.0500