Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Jan. 31, 2017
Property Plant And Equipment [Line Items]
Total property and equipment	$ 204,323	$ 175,302
Less: accumulated depreciation and amortization	(122,473)	(93,607)
Property and equipment, net	81,850	81,695
Test equipment
Property Plant And Equipment [Line Items]
Total property and equipment	125,348	105,955
Computer equipment and software
Property Plant And Equipment [Line Items]
Total property and equipment	60,838	54,521
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	5,045	4,494
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 13,092	$ 10,332