Investments and Fair Value Measurements - Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 93,509	$ 114,870
Gross Unrealized Gain	607	98
Gross Unrealized Loss	(32)	(1)
Fair Value	94,084	114,967
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,051	17,462
Gross Unrealized Gain	0	9
Gross Unrealized Loss	(27)	(1)
Fair Value	9,024	17,470
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,498	5,481
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	2,498	5,481
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	68,106	78,075
Gross Unrealized Gain	607	85
Gross Unrealized Loss	0	0
Fair Value	68,713	78,160
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,854	13,852
Gross Unrealized Gain	0	4
Gross Unrealized Loss	(5)	0
Fair Value	$ 13,849	$ 13,856

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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Amortized cost 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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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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