Significant Balance Sheet Components - Prepaid royalties, Accrued expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued commissions	$ 4,303	$ 4,810
Accrued stock-settled bonus	5,719	6,875
Employee Stock Purchase Plan liability	1,982	2,187
Other accrued payroll-related expenses	3,399	2,839
Accrued royalties	3,256	2,386
Other accrued liabilities	6,050	5,695
Total accrued expenses	24,709	24,792
Prepaid expenses and other current assets
Prepaid royalties	7,400	6,300
Other assets
Prepaid royalties	$ 2,000	$ 3,000