Securities - Schedule of Available-for-Sales Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,301,271	$ 1,293,239
Gross Unrealized Gains	35,510	10,466
Gross Unrealized Losses	1,628	5,118
Fair Value	1,335,153	1,298,587
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	400	1,840
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	400	1,840
Obligations of U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	268,024	367,551
Gross Unrealized Gains	11,495	5,021
Gross Unrealized Losses	20	84
Fair Value	279,499	372,488
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	119,703	96,668
Gross Unrealized Gains	2,743	1,178
Gross Unrealized Losses	60	61
Fair Value	122,386	97,785
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	206,017	164,643
Gross Unrealized Gains	3,271	1,327
Gross Unrealized Losses	941	1,519
Fair Value	208,347	164,451
U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	704,627	660,037
Gross Unrealized Gains	18,001	2,940
Gross Unrealized Losses	471	3,387
Fair Value	722,157	659,590
U.S. corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,500	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	136	67
Fair Value	$ 2,364	$ 2,433