Shareholders' Equity - Schedule of Minimum Required Capital Amounts and Ratios for Well Capitalized Institutions and The Actual Capital Amounts and Ratios for The Company and The Bank (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Minimum required capital amounts and ratios for well capitalized institutions and the actual capital amounts [Line Items]
Shareholders’ Equity	$ 1,374,507	$ 1,286,832	$ 1,268,200	$ 1,231,868
Well Capitalized Minimum Common Equity Tier One Ratio (as a percent)	6.50%	6.50%
Well Capitalized Minimum Tier 1 Capital Ratio (as a percent)	8.0	8.0
Well Capitalized Minimum Total Capital Ratio (as a percent)	10.0	10.0
Well Capitalized Minimum Tier 1 Leverage Ratio (as a percent)	5.0	5.0
Parent [Member]
Minimum required capital amounts and ratios for well capitalized institutions and the actual capital amounts [Line Items]
Shareholders’ Equity	$ 1,374,507	$ 1,286,832
Common Equity Tier One Capital	1,361,915	1,289,424
Tier 1 Capital	1,361,915	1,289,424
Total Capital	$ 1,503,784	$ 1,406,273
Common Equity Tier One Capital Ratio	12.06%	12.18%
Tier 1 Capital Ratio (as a percent)	12.06	12.18
Total Capital Ratio (as a percent)	13.31	13.28
Tier 1 Leverage Ratio (as a percent)	6.71	7.25
Subsidiaries [Member]
Minimum required capital amounts and ratios for well capitalized institutions and the actual capital amounts [Line Items]
Shareholders’ Equity	$ 1,290,455	$ 1,229,775
Common Equity Tier One Capital	1,289,435	1,243,939
Tier 1 Capital	1,289,435	1,243,939
Total Capital	$ 1,431,106	$ 1,360,788
Common Equity Tier One Capital Ratio	11.43%	11.76%
Tier 1 Capital Ratio (as a percent)	11.43	11.76
Total Capital Ratio (as a percent)	12.69	12.87
Tier 1 Leverage Ratio (as a percent)	6.35	7.01