Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016	Jan. 31, 2017
Property Plant And Equipment [Line Items]
Accumulated depreciation of property and equipment acquired under capital lease	$ 23.6		$ 23.6		$ 10.4
Depreciation expense	9.9	$ 8.2	28.8	$ 28.6
Servers
Property Plant And Equipment [Line Items]
Gross amount of property and equipment acquired under capital lease	65.3		65.3		43.2
Depreciation expense	4.9	$ 2.0	13.3	$ 5.0
Construction in progress
Property Plant And Equipment [Line Items]
Gross amount of property and equipment acquired under capital lease	$ 6.8		$ 6.8		$ 5.6