Investment Securities - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,007,834	$ 1,187,499
Gross Unrealized/Unrecognized Holding Gains	52,235	28,425
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	728	6,223
Debt Securities, Available-for-sale	1,059,341	1,209,701
Obligations of States and Political Subdivisions
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	279,245	302,928
Gross Unrealized/Unrecognized Holding Gains	25,973	17,563
Debt Securities, Available-for-sale	305,218	320,491
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	726,589	884,571
Gross Unrealized/Unrecognized Holding Gains	26,248	10,862
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	728	6,223
Debt Securities, Available-for-sale	752,109	$ 889,210
Corporate Debt Securities
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,000
Gross Unrealized/Unrecognized Holding Gains	14
Debt Securities, Available-for-sale	$ 2,014

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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