Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Jan. 31, 2018
Property Plant And Equipment [Line Items]
Accumulated depreciation of property and equipment acquired under capital lease	$ 47.1		$ 47.1		$ 29.1
Depreciation expense	11.4	$ 9.9	34.7	$ 28.8
Capitalized qualifying implementation costs incurred for service contract	1.6		1.6
Other Long-Term Assets
Property Plant And Equipment [Line Items]
Capitalized qualifying costs to develop software for internal use	1.3		1.3
Servers
Property Plant And Equipment [Line Items]
Gross amount of property and equipment acquired under capital lease	100.7		100.7		74.7
Depreciation expense	6.6	$ 4.9	19.0	$ 13.3
Construction in progress
Property Plant And Equipment [Line Items]
Gross amount of property and equipment acquired under capital lease	$ 5.7		$ 5.7		$ 3.7