Investments - Schedule of Available-for-sale and Held-to-Maturity Securities Reconciliation (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	$ 451,114	$ 488,059
Gross Unrealized Gains	8,942	13,960
Gross Unrealized Losses	(1,031)	(496)
Allowance for Credit Losses	(449)	(449)
Fair Value	459,025	501,523
Total securities held-to-maturity, net	450,665	487,610
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	1,065,223	882,682
Gross Unrealized Gains	21,824	30,104
Gross Unrealized Losses	(2,824)	(357)
Fair Value	1,084,223	912,429
Obligations of U.S. Government-sponsored enterprises
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	99,490	14,978
Gross Unrealized Gains	93	186
Gross Unrealized Losses	(329)	(3)
Fair Value	99,254	15,161
Obligations of states and political subdivisions
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	240,163	248,324
Gross Unrealized Gains	1,845	2,814
Gross Unrealized Losses	(763)	0
Fair Value	241,245	251,138
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	475,710	335,271
Gross Unrealized Gains	6,328	8,994
Gross Unrealized Losses	(1,193)	(33)
Fair Value	480,845	344,232
Agency mortgage-backed securities
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	84,544	112,742
Gross Unrealized Gains	1,403	2,295
Gross Unrealized Losses	(268)	(496)
Fair Value	85,679	114,541
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	464,288	506,703
Gross Unrealized Gains	14,393	20,190
Gross Unrealized Losses	(1,302)	(321)
Fair Value	477,379	526,572
U.S. Treasury bills
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	10,985	10,980
Gross Unrealized Gains	361	486
Gross Unrealized Losses	0	0
Fair Value	11,346	11,466
Corporate debt securities
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	126,407	126,993
Gross Unrealized Gains	5,694	8,851
Gross Unrealized Losses	0	0
Fair Value	132,101	135,844
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	14,750	14,750
Gross Unrealized Gains	649	248
Gross Unrealized Losses	0	0
Fair Value	$ 15,399	$ 14,998

Debt Securities, Held-To-Maturity, Net Of Allowance For Credit Losses

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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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