Securities, Available-for-sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-for-sale [Abstract]
Amortized cost	$ 1,150,224	$ 978,774
Gross unrealized gains	14,752	19,273
Gross unrealized losses	(9,781)	(786)
Fair value	1,155,195	997,261
U.S. Treasury and Government Agencies [Member]
Available-for-sale [Abstract]
Amortized cost	205,355	148,507
Gross unrealized gains	419	483
Gross unrealized losses	(2,155)	(197)
Fair value	203,619	148,793
State and Political Subdivisions [Member]
Available-for-sale [Abstract]
Amortized cost	219,389	133,287
Gross unrealized gains	5,416	7,132
Gross unrealized losses	(4,688)	(3)
Fair value	220,117	140,416
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale [Abstract]
Amortized cost	669,134	640,537
Gross unrealized gains	8,616	11,648
Gross unrealized losses	(2,918)	(378)
Fair value	674,832	651,807
Other Debt Securities [Member]
Available-for-sale [Abstract]
Amortized cost	56,346	56,443
Gross unrealized gains	301	10
Gross unrealized losses	(20)	(208)
Fair value	$ 56,627	$ 56,245

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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