Condensed Consolidated Balance Sheet Components - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued royalty obligations	$ 853	$ 707
Accrued legal expenses	2,400	814
Accrued tax liabilities	1,410	1,470
Accrued professional services	1,988	1,791
Purchases of property and equipment included in accrued expenses	137	343
Other	2,349	1,956
Total accrued expenses	$ 9,137	$ 7,081