Investment Securities - Schedule of AFS Debt Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 165,159	$ 465,117
Less Than 12 Months, Gross Unrealized Losses	(876)	(2,189)
12 Months or Longer, Fair Value	318,953	474,384
12 Months or Longer, Gross Unrealized Losses	(1,499)	(7,587)
Total Fair Value	484,112	939,501
Total Gross Unrealized Losses	(2,375)	(9,776)
Debt Securities Issued by the U.S. Treasury and Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	87,070	65,479
Less Than 12 Months, Gross Unrealized Losses	(549)	(188)
12 Months or Longer, Fair Value	21,338	101,761
12 Months or Longer, Gross Unrealized Losses	(42)	(1,259)
Total Fair Value	108,408	167,240
Total Gross Unrealized Losses	(591)	(1,447)
Debt Securities Issued by States and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	26	6,788
Less Than 12 Months, Gross Unrealized Losses	(1)	(14)
12 Months or Longer, Fair Value		440
Total Fair Value	26	7,228
Total Gross Unrealized Losses	(1)	(14)
Debt Securities Issued by Corporations
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	50,000	25,892
Less Than 12 Months, Gross Unrealized Losses	(103)	(326)
12 Months or Longer, Fair Value	65,000	74,693
12 Months or Longer, Gross Unrealized Losses	(853)	(307)
Total Fair Value	115,000	100,585
Total Gross Unrealized Losses	(956)	(633)
Residential - Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	28,063	119,271
Less Than 12 Months, Gross Unrealized Losses	(223)	(526)
12 Months or Longer, Fair Value	113,538	170,805
12 Months or Longer, Gross Unrealized Losses	(222)	(2,741)
Total Fair Value	141,601	290,076
Total Gross Unrealized Losses	(445)	(3,267)
Residential - U.S. Government-Sponsored Enterprises
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value		187,861
Less Than 12 Months, Gross Unrealized Losses		(816)
12 Months or Longer, Fair Value	94,002	73,720
12 Months or Longer, Gross Unrealized Losses	(324)	(1,058)
Total Fair Value	94,002	261,581
Total Gross Unrealized Losses	(324)	(1,874)
Commercial - Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value		59,826
Less Than 12 Months, Gross Unrealized Losses		(319)
12 Months or Longer, Fair Value	25,075	52,965
12 Months or Longer, Gross Unrealized Losses	(58)	(2,222)
Total Fair Value	25,075	112,791
Total Gross Unrealized Losses	(58)	(2,541)
Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	28,063	366,958
Less Than 12 Months, Gross Unrealized Losses	(223)	(1,661)
12 Months or Longer, Fair Value	232,615	297,490
12 Months or Longer, Gross Unrealized Losses	(604)	(6,021)
Total Fair Value	260,678	664,448
Total Gross Unrealized Losses	$ (827)	$ (7,682)