Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued payroll and related expenses	$ 18,447		$ 26,108
Accrued professional fees	4,229		4,734
Accrued taxes	1,970		2,827
Accrued clinical and research expenses	740		1,279
Accrued interest	243		243
Accrued warranty	943	$ 820	708	$ 656	$ 628	$ 645
Accrued other	3,320		3,491
Total accrued liabilities	$ 29,892		$ 39,390