Securities - Schedule of Available-for-Sales Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,009,317	$ 1,599,894
Gross Unrealized Gains	21,932	30,773
Gross Unrealized Losses	17,160	3,474
Fair Value	2,014,089	1,627,193
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	129,228
Gross Unrealized Gains	138
Gross Unrealized Losses	275
Fair Value	129,091
Obligations of U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	824,157	599,652
Gross Unrealized Gains	7,534	9,820
Gross Unrealized Losses	7,973	1,992
Fair Value	823,718	607,480
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	111,269	126,642
Gross Unrealized Gains	2,599	3,144
Gross Unrealized Losses	79	40
Fair Value	113,789	129,746
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	113,357	179,538
Gross Unrealized Gains	1,782	3,216
Gross Unrealized Losses	717	646
Fair Value	114,422	182,108
U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	828,806	691,562
Gross Unrealized Gains	9,879	14,593
Gross Unrealized Losses	8,029	675
Fair Value	830,656	705,480
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	87	121
Fair Value	$ 2,413	$ 2,379

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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