Securities, Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale [Abstract]
Amortized cost	$ 931,919	$ 593,945
Gross unrealized gains	18,652	7,860
Gross unrealized losses	(1,482)	(1,961)
Fair value	949,089	599,844
U.S. Treasury and Government Agencies [Member]
Available-for-sale [Abstract]
Amortized cost	85,095	171,250
Gross unrealized gains	535	476
Gross unrealized losses	(249)	(576)
Fair value	85,381	171,150
State and Political Subdivisions [Member]
Available-for-sale [Abstract]
Amortized cost	124,997	99,403
Gross unrealized gains	6,334	2,941
Gross unrealized losses	(26)	(37)
Fair value	131,305	102,307
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale [Abstract]
Amortized cost	665,331	291,874
Gross unrealized gains	11,783	4,443
Gross unrealized losses	(240)	(1,072)
Fair value	676,874	295,245
Other Debt Securities [Member]
Available-for-sale [Abstract]
Amortized cost	56,496	31,418
Gross unrealized gains	0	0
Gross unrealized losses	(967)	(276)
Fair value	$ 55,529	$ 31,142

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 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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