Investments and Fair Value Measurements - Schedule of Marketable Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cost	$ 169,408	$ 241,853
Gross Unrealized Gains	1,028	130
Gross Unrealized Losses	(3)	(10)
Fair Value	170,433	241,973
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Cost	161	161
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	161	162
U.S. treasury
Debt Securities, Available-for-sale [Line Items]
Cost	48,502	31,933
Gross Unrealized Gains	393	8
Gross Unrealized Losses	0	(1)
Fair Value	48,895	31,940
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Cost	98,955	177,629
Gross Unrealized Gains	597	110
Gross Unrealized Losses	0	(9)
Fair Value	99,552	177,730
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cost	12,553	15,240
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	12,553	15,240
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Cost	6,357	3,014
Gross Unrealized Gains	35	1
Gross Unrealized Losses	0	0
Fair Value	6,392	3,015
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Cost	2,880	13,876
Gross Unrealized Gains	3	10
Gross Unrealized Losses	(3)	0
Fair Value	$ 2,880	$ 13,886

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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