Securities - Schedule of Available-for-Sales Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	$ 1,941,284	$ 1,599,894
Gross Unrealized Gains	22,511	30,773
Gross Unrealized Losses	28,980	3,474
Fair Value	1,934,815	1,627,193
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	29,634
Gross Unrealized Gains	0
Gross Unrealized Losses	523
Fair Value	29,111
Obligations of U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	793,360	599,652
Gross Unrealized Gains	8,063	9,820
Gross Unrealized Losses	13,636	1,992
Fair Value	787,787	607,480
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	117,242	126,642
Gross Unrealized Gains	2,286	3,144
Gross Unrealized Losses	207	40
Fair Value	119,321	129,746
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	141,110	179,538
Gross Unrealized Gains	2,163	3,216
Gross Unrealized Losses	1,069	646
Fair Value	142,204	182,108
U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	857,438	691,562
Gross Unrealized Gains	9,999	14,593
Gross Unrealized Losses	13,461	675
Fair Value	853,976	705,480
U.S. corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, at amortized cost	2,500	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	84	121
Fair Value	$ 2,416	$ 2,379