Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Jan. 31, 2018
Property Plant And Equipment [Line Items]
Total property and equipment	$ 278,148	$ 235,035
Less: accumulated depreciation and amortization	(176,430)	(145,893)
Property and equipment, net	101,718	89,142	[1]
Test equipment
Property Plant And Equipment [Line Items]
Total property and equipment	156,040	142,311
Computer equipment and software
Property Plant And Equipment [Line Items]
Total property and equipment	92,863	72,329
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	5,482	5,363
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 23,763	$ 15,032

[1] *Prior period information has been adjusted to reflect the adoption impact of Accounting Standards Codification 606, Revenue from Contracts with Customers (ASC 606), which we adopted on February 1, 2018.