Securities - Summary of Gross Unrealized Losses and Fair Values, Aggregated by Investment Category and Length of Individual Securities Continuous Unrealized Loss Position Available-for-sale (Details) $ in Thousands	Sep. 30, 2020 USD ($) Security	Dec. 31, 2019 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	41	99
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 258,799	$ 343,722
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(1,735)	(2,377)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	19,703	257,869
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	(626)	(2,328)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	278,502	601,591
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses	$ (2,361)	$ (4,705)
U.S. Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	7	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 50,779	$ 49,318
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(357)	(662)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		20,283
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses		(92)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	50,779	69,601
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses	$ (357)	$ (754)
Obligations of States, Municipalities, and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	1	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 126	$ 13,309
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses		(45)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		1,419
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses		(4)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	$ 126	14,728
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses		$ (49)
Agency, Residential Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	11	50
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 116,877	$ 132,703
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(349)	(666)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	503	193,363
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	(6)	(1,688)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	117,380	326,066
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses	$ (355)	$ (2,354)
Non-Agency, Residential Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security		9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		$ 36,902
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses		(206)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		10,126
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses		(66)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value		47,028
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses		$ (272)
Agency, Commercial Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	7	13
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 59,474	$ 67,649
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(513)	(563)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		32,678
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses		(478)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	59,474	100,327
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses	$ (513)	$ (1,041)
Corporate Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	7	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 12,304	$ 6,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(215)	(37)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	12,304	6,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses	$ (215)	$ (37)
Asset-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security	8	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 19,239	$ 37,738
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(301)	(198)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	19,200
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	(620)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	38,439	37,738
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses	$ (921)	$ (198)