Balance Sheet Components - Other Assets (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
	Aug. 08, 2017	Apr. 30, 2016	Mar. 31, 2018	Dec. 31, 2017	Aug. 14, 2017
Balance Sheet Components [Line Items]
Agreement term		4 years
Total consideration		$ 3,200
Deferred costs included in other long-term assets			$ 1,600	$ 1,800
Amortization of deferred costs			$ 200
Common stock, shares issued			54,251,000	54,040,000
Debt discount			$ 600
Noncurrent assets			3,912	$ 3,979
2017 Term Loan
Balance Sheet Components [Line Items]
Common stock, shares issued					300,000
Payments of debt issuance costs	$ 300
Debt discount	2,700
Debt instrument, fee amount	2,400
Remaining borrowing capacity	25,000
2017 Term Loan | Direct reduction from outstanding debt balance
Balance Sheet Components [Line Items]
Debt instrument, fee amount	2,000		$ 1,900
2017 Term Loan | Noncurrent assets
Balance Sheet Components [Line Items]
Debt instrument, fee amount	$ 700