Investment Securities - Investment securities and summary of the gains (losses) related to securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available for sale securities:
Amortized Cost	$ 185,491	$ 252,958
Unrealized gains	4,435	3,315
Unrealized losses	(9)	(5)
Fair value	189,917	256,268
Commercial paper
Available for sale securities:
Amortized Cost	9,720	1,976
Unrealized gains	3	1
Unrealized losses	(9)
Fair value	9,714	1,977
Corporate bonds
Available for sale securities:
Amortized Cost	175,771	250,982
Unrealized gains	4,432	3,314
Unrealized losses		(5)
Fair value	$ 180,203	$ 254,291

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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Amount 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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