Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Apr. 30, 2017	Jan. 31, 2017
Property Plant And Equipment [Line Items]
Total property and equipment	$ 190,211	$ 175,302
Less: accumulated depreciation and amortization	(107,918)	(93,607)
Property and equipment, net	82,293	81,695
Test equipment
Property Plant And Equipment [Line Items]
Total property and equipment	116,629	105,955
Computer equipment and software
Property Plant And Equipment [Line Items]
Total property and equipment	57,453	54,521
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	4,691	4,494
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 11,438	$ 10,332