Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued payroll and related expenses	$ 26,792	$ 26,108
Accrued professional fees	1,595	4,734
Accrued taxes	2,506	2,827
Accrued clinical and research expenses	1,105	1,279
Accrued interest	243	243
Accrued warranty	1,236	708	$ 645
Accrued other	5,313	3,491
Total accrued liabilities	$ 38,790	$ 39,390