Investment Securities - Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Mortgage-backed securities
Investment securities
Fair value, less than twelve months	$ 0	$ 0
Gross unrealized losses, less than twelve months	0	0
Fair value, twelve months or greater	0	2,115
Gross unrealized losses, twelve months or greater	0	(46)
Fair value, total	0	2,115
Gross unrealized losses, total	0	(46)
State and political securities
Investment securities
Fair value, less than twelve months	4,179	7,958
Gross unrealized losses, less than twelve months	(6)	(40)
Fair value, twelve months or greater	904	224
Gross unrealized losses, twelve months or greater	(7)	(37)
Fair value, total	5,083	8,182
Gross unrealized losses, total	(13)	(77)
Other debt securities
Investment securities
Fair value, less than twelve months	9,682	13,373
Gross unrealized losses, less than twelve months	(260)	(216)
Fair value, twelve months or greater	3,271	14,258
Gross unrealized losses, twelve months or greater	(237)	(310)
Fair value, total	12,953	27,631
Gross unrealized losses, total	(497)	(526)
Total debt securities
Investment securities
Fair value, less than twelve months	13,861	21,331
Gross unrealized losses, less than twelve months	(266)	(256)
Fair value, twelve months or greater	4,175	16,597
Gross unrealized losses, twelve months or greater	(244)	(393)
Fair value, total	18,036	37,928
Gross unrealized losses, total	$ (510)	$ (649)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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