Significant Balance Sheet Components - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Expenses [Abstract]
Accrued commissions	$ 2,775	$ 3,989
Accrued stock-settled bonus	2,469	7,705
Employee Stock Purchase Plan liability	778	2,047
Other accrued payroll-related expenses	3,383	4,285
Other accrued liabilities	6,714	7,044
Total accrued expenses	$ 16,119	$ 25,070