Cash Equivalents and Investments (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)
Marketable Securities [Line Items]
Amortized Cost	$ 75,515
Gains	0
Losses	(39)
Fair Value	75,476
Cash equivalents
Marketable Securities [Line Items]
Fair Value	10,838
Short-term investments
Marketable Securities [Line Items]
Fair Value	64,638
Money market funds
Marketable Securities [Line Items]
Amortized Cost	5,838
Gains	0
Losses	0
Fair Value	5,838
Repurchase agreements
Marketable Securities [Line Items]
Payments to Acquire Debt Securities, Available-for-sale	5,000
Amortized Cost	5,000
Gains	0
Losses	0
Fair Value	5,000
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	30,710
Gains	0
Losses	0
Fair Value	30,710
Corporate notes
Marketable Securities [Line Items]
Amortized Cost	13,168
Gains	0
Losses	(24)
Fair Value	13,144
U.S. government securities
Marketable Securities [Line Items]
Amortized Cost	10,167
Gains	0
Losses	(1)
Fair Value	10,166
U.S. asset-backed securities
Marketable Securities [Line Items]
Amortized Cost	10,632
Gains	0
Losses	(14)
Fair Value	$ 10,618

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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