Securities - Schedule of Unrealized Loss and Fair Value on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value
Less Than 12 Months	$ 742,721	$ 332,099
12 Months or Longer	27,767	73,338
Total	770,488	405,437
Unrealized Losses
Less Than 12 Months	(9,017)	(1,530)
12 Months or Longer	(833)	(568)
Total	(9,850)	(2,098)
U.S. Treasury securities and obligations of U.S. government agencies
Fair Value
Less Than 12 Months	0	0
12 Months or Longer	248	256
Total	248	256
Unrealized Losses
Less Than 12 Months	0	0
12 Months or Longer	(2)	(1)
Total	(2)	(1)
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Fair Value
Less Than 12 Months	660,028	203,405
12 Months or Longer	15,350	569
Total	675,378	203,974
Unrealized Losses
Less Than 12 Months	(8,696)	(1,218)
12 Months or Longer	(754)	(22)
Total	(9,450)	(1,240)
Private mortgage-backed securities and collateralized mortgage obligations
Fair Value
Less Than 12 Months	13,018	23,997
12 Months or Longer	2,710	0
Total	15,728	23,997
Unrealized Losses
Less Than 12 Months	(206)	(210)
12 Months or Longer	(30)	0
Total	(236)	(210)
Collateralized loan obligations
Fair Value
Less Than 12 Months	64,232	104,697
12 Months or Longer	9,459	72,513
Total	73,691	177,210
Unrealized Losses
Less Than 12 Months	(58)	(102)
12 Months or Longer	(47)	(545)
Total	(105)	$ (647)
Obligations of state and political subdivisions
Fair Value
Less Than 12 Months	5,443
12 Months or Longer	0
Total	5,443
Unrealized Losses
Less Than 12 Months	(57)
12 Months or Longer	0
Total	$ (57)