Securities - Schedule of Unrealized Loss and Fair Value on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Fair Value
Less Than 12 Months	$ 349,558		$ 312,988
12 Months or Longer	111,109		214,951
Total	460,667		527,939
Unrealized Losses
Less Than 12 Months	(1,722)		(2,041)
12 Months or Longer	(1,933)		(2,506)
Total	(3,655)		(4,547)
U.S. Treasury securities and obligations of U.S. government agencies
Fair Value
Less Than 12 Months	0		758
12 Months or Longer	258		0
Total	258		758
Unrealized Losses
Less Than 12 Months	0		(4)
12 Months or Longer	(1)		0
Total	(1)		(4)
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Fair Value
Less Than 12 Months	248,463		220,057
12 Months or Longer	351		104,184
Total	248,814		324,241
Unrealized Losses
Less Than 12 Months	(628)		(1,461)
12 Months or Longer	(18)		(1,923)
Total	(646)		(3,384)
Private mortgage-backed securities and collateralized mortgage obligations
Fair Value
Less Than 12 Months	28,276		2,978
12 Months or Longer	0		0
Total	28,276		2,978
Unrealized Losses
Less Than 12 Months	(298)		(5)
12 Months or Longer	0		0
Total	(298)		(5)
Collateralized loan obligations
Fair Value
Less Than 12 Months	66,037		88,680
12 Months or Longer	110,500		110,767
Total	176,537		199,447
Unrealized Losses
Less Than 12 Months	(699)		(570)
12 Months or Longer	(1,914)		(583)
Total	(2,613)	$ (1,200)	(1,153)
Obligations of state and political subdivisions
Fair Value
Less Than 12 Months	6,782		515
12 Months or Longer	0		0
Total	6,782		515
Unrealized Losses
Less Than 12 Months	(97)		(1)
12 Months or Longer	0		0
Total	$ (97)		$ (1)