Cash Equivalents and Investments - Schedule of Fair Value of Securities (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 75,180
Gains	0
Losses	(18)
Fair Value	75,162
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Fair Value	30,700
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Fair Value	44,462
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	18,684
Gains	0
Losses	0
Fair Value	18,684
Repurchase agreements
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,002
Gains	0
Losses	0
Fair Value	10,002
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	21,832
Gains	0
Losses	0
Fair Value	21,832
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,058
Gains	0
Losses	(11)
Fair Value	13,047
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,174
Gains	0
Losses	(1)
Fair Value	3,173
U.S. asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,430
Gains	0
Losses	(6)
Fair Value	$ 8,424

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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