Balance Sheet Components - Other Assets (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Aug. 14, 2017	Apr. 30, 2016
Balance Sheet Components [Line Items]
Agreement term		4 years
Total consideration					$ 3,200
Deferred costs included in other long-term assets		$ 1,800	$ 2,600
Amortization of deferred costs		$ 800	$ 600
Common stock, shares issued		54,040,000	52,665,000
Payments of debt issuance costs		$ 287
Noncurrent assets		3,979	$ 3,934
2017 Term Loan
Balance Sheet Components [Line Items]
Common stock, shares issued	300,000			300,000
Debt discount	$ 2,700	$ 600
Debt, increase (decrease)	(2,000)
Debt instrument, fee amount	2,400
Noncurrent assets	700
Remaining borrowing capacity	$ 25,000