Securities - Schedule of Unrealized Loss and Fair Value on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value
Less Than 12 Months	$ 210,255	$ 478,423
12 Months or Longer	226,061	646,354
Total	436,316	1,124,777
Unrealized Losses
Less Than 12 Months	(969)	(7,140)
12 Months or Longer	(2,476)	(19,538)
Total	(3,445)	(26,678)
U.S. Treasury securities and obligations of U.S. government agencies
Fair Value
Less Than 12 Months	438	99
12 Months or Longer	0	642
Total	438	741
Unrealized Losses
Less Than 12 Months	(1)	(1)
12 Months or Longer	0	(5)
Total	(1)	(6)
Mortgage-backed securities and collateralized mortgage obligations of U.S. government sponsored entities
Fair Value
Less Than 12 Months	83,139	200,184
12 Months or Longer	115,545	623,420
Total	198,684	823,604
Unrealized Losses
Less Than 12 Months	(383)	(2,235)
12 Months or Longer	(1,642)	(19,136)
Total	(2,025)	(21,371)
Private mortgage-backed securities and collateralized mortgage obligations
Fair Value
Less Than 12 Months	8,010	20,071
12 Months or Longer	0	12,739
Total	8,010	32,810
Unrealized Losses
Less Than 12 Months	(17)	(344)
12 Months or Longer	0	(187)
Total	(17)	(531)
Collateralized loan obligations
Fair Value
Less Than 12 Months	118,668	238,894
12 Months or Longer	110,516	0
Total	229,184	238,894
Unrealized Losses
Less Than 12 Months	(568)	(4,319)
12 Months or Longer	(834)	0
Total	$ (1,402)	(4,319)
Obligations of state and political subdivisions
Fair Value
Less Than 12 Months		19,175
12 Months or Longer		9,553
Total		28,728
Unrealized Losses
Less Than 12 Months		(241)
12 Months or Longer		(210)
Total		$ (451)