Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Jan. 31, 2018
Property Plant And Equipment [Line Items]
Total property and equipment	$ 254,291	$ 235,035
Less: accumulated depreciation and amortization	(160,011)	(145,893)
Property and equipment, net	94,280	89,142	[1]
Test equipment
Property Plant And Equipment [Line Items]
Total property and equipment	148,444	142,311
Computer equipment and software
Property Plant And Equipment [Line Items]
Total property and equipment	82,102	72,329
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	5,611	5,363
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 18,134	$ 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.