Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Jan. 31, 2017
Property Plant And Equipment [Line Items]
Accumulated depreciation of property and equipment acquired under capital lease	$ 14.3		$ 10.4
Depreciation expense	9.2	$ 10.6
Servers
Property Plant And Equipment [Line Items]
Gross amount of property and equipment acquired under capital lease	50.5		43.2
Depreciation expense	3.8	$ 1.3
Construction in progress
Property Plant And Equipment [Line Items]
Gross amount of property and equipment acquired under capital lease	$ 8.4		$ 5.6