Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related expenses	$ 9,151		$ 5,157
Provision for sales returns	2,419		1,862
Accrued professional services	682		1,014
Operating lease liability	769
Accrued royalty expense	470		313
Deferred revenue	304		137
Accrued travel expenses	431		270
Accrued clinical expenses	241		244
Accrued other expenses	567		451
Accrued liabilities	$ 15,034	$ 721	$ 9,448