Commitments and Contingencies - Additional Information (Details)		1 Months Ended		12 Months Ended
	Oct. 18, 2016 USD ($)	Mar. 31, 2018 USD ($) ft²	Aug. 31, 2017 USD ($) ft²	Jan. 31, 2018 USD ($)	Jan. 31, 2017 USD ($)	Jan. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Aggregate future minimum payments under non-cancelable operating leases				$ 112,999,000
Rent expense recognized under operating leases				19,400,000	$ 16,600,000	$ 11,000,000
Non-cancelable purchase obligation related to software services				26,800,000	4,100,000
Outstanding letters of credit				9,600,000	$ 7,700,000
Loss contingency				$ 0
Dell
Loss Contingencies [Line Items]
Loss contingency, damages awarded, value	$ 30,000,000
Mountain View, California
Loss Contingencies [Line Items]
Lessee, operating lease, term of contract			7 years
Lessee, operating lease, area of property (in sqft) | ft²			45,831
Aggregate future minimum payments under non-cancelable operating leases			$ 32,200,000
Mountain View, California | Letter of Credit
Loss Contingencies [Line Items]
Debt instrument, face amount			$ 2,600,000.0
Mountain View, California | Subsequent Event
Loss Contingencies [Line Items]
Lessee, operating lease, term of contract		10 years
Lessee, operating lease, area of property (in sqft) | ft²		31,571
Aggregate future minimum payments under non-cancelable operating leases		$ 34,800,000
Mountain View, California | Subsequent Event | Letter of Credit
Loss Contingencies [Line Items]
Debt instrument, face amount		$ 1,500,000.0