Securities - Fair Value of Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Available for sale
Amortized Cost	$ 899,541	$ 822,089
Gross Unrealized Gains	36,364	15,961
Gross Unrealized Losses	(765)	(3,274)
Fair Value	935,140	834,776
Held to maturity
Amortized Cost	190,935	207,899
Gross Unrealized Gains	10,883	7,336
Gross Unrealized Losses	0	(88)
Fair Value	201,818	215,147
U.S. Treasury and federal agencies
Available for sale
Amortized Cost		1,415
Gross Unrealized Gains		0
Gross Unrealized Losses		(2)
Fair Value		1,413
State and municipal
Available for sale
Amortized Cost	525,488	396,931
Gross Unrealized Gains	23,503	11,288
Gross Unrealized Losses	(759)	(2,451)
Fair Value	548,232	405,768
Held to maturity
Amortized Cost	175,953	190,767
Gross Unrealized Gains	10,408	7,129
Gross Unrealized Losses	0	(54)
Fair Value	186,361	197,842
Federal agency collateralized mortgage obligations
Available for sale
Amortized Cost	219,431	267,272
Gross Unrealized Gains	6,380	2,543
Gross Unrealized Losses	(6)	(563)
Fair Value	225,805	269,252
Held to maturity
Amortized Cost	3,006	4,560
Gross Unrealized Gains	89	13
Gross Unrealized Losses	0	(5)
Fair Value	3,095	4,568
Federal agency mortgage-backed pools
Available for sale
Amortized Cost	143,755	145,623
Gross Unrealized Gains	5,031	1,207
Gross Unrealized Losses	0	(258)
Fair Value	148,786	146,572
Held to maturity
Amortized Cost	11,976	12,572
Gross Unrealized Gains	386	194
Gross Unrealized Losses	0	(29)
Fair Value	12,362	12,737
Corporate notes
Available for sale
Amortized Cost	10,867	10,848
Gross Unrealized Gains	1,450	923
Gross Unrealized Losses	0	0
Fair Value	$ 12,317	$ 11,771

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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