Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Oct. 31, 2017	Jan. 31, 2017
Property Plant And Equipment [Line Items]
Total property and equipment	$ 220,919	$ 175,302
Less: accumulated depreciation and amortization	(136,655)	(93,607)
Property and equipment, net	84,264	81,695
Test equipment
Property Plant And Equipment [Line Items]
Total property and equipment	135,497	105,955
Computer equipment and software
Property Plant And Equipment [Line Items]
Total property and equipment	66,270	54,521
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	5,337	4,494
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 13,815	$ 10,332