Securities - Schedule of Unrealized Loss and Fair Value on Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value
Less than 12 months	$ 312,988	$ 478,423
12 months or longer	214,951	646,354
Total	527,939	1,124,777
Unrealized Losses
Less than 12 months	(2,041)	(7,140)
12 months or longer	(2,506)	(19,538)
Total	(4,547)	(26,678)
U.S. Treasury securities and obligations of U.S. government agencies
Fair Value
Less than 12 months	758	99
12 months or longer	0	642
Total	758	741
Unrealized Losses
Less than 12 months	(4)	(1)
12 months or longer	0	(5)
Total	(4)	(6)
Mortgage-backed securities and collateralized mortgage obligations of U.S. government sponsored entities
Fair Value
Less than 12 months	220,057	200,184
12 months or longer	104,184	623,420
Total	324,241	823,604
Unrealized Losses
Less than 12 months	(1,461)	(2,235)
12 months or longer	(1,923)	(19,136)
Total	(3,384)	(21,371)
Private mortgage-backed securities and collateralized mortgage obligations
Fair Value
Less than 12 months	2,978	20,071
12 months or longer	0	12,739
Total	2,978	32,810
Unrealized Losses
Less than 12 months	(5)	(344)
12 months or longer	0	(187)
Total	(5)	(531)
Collateralized loan obligations
Fair Value
Less than 12 months	88,680	238,894
12 months or longer	110,767	0
Total	199,447	238,894
Unrealized Losses
Less than 12 months	(570)	(4,319)
12 months or longer	(583)	0
Total	(1,153)	(4,319)
Obligations of state and political subdivisions
Fair Value
Less than 12 months	515	19,175
12 months or longer	0	9,553
Total	515	28,728
Unrealized Losses
Less than 12 months	(1)	(241)
12 months or longer	0	(210)
Total	$ (1)	$ (451)