Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017	Jan. 31, 2018	Nov. 27, 2017
Commitments And Contingencies [Line Items]
Non-cancellable sublease expiration year			2023
Rent expense	$ 8.3	$ 6.9	$ 16.6	$ 12.2
Sublease income	2.1	$ 1.9	4.0	$ 3.7
Subleases Expire in Fiscal 2018 and 2023
Commitments And Contingencies [Line Items]
Non-cancellable sublease proceeds for the year ending January 31, 2019	3.8		3.8
Non-cancellable sublease proceeds for the year ending January 31, 2020	7.7		7.7
Non-cancellable sublease proceeds for the year ending January 31, 2021	7.0		7.0
Non-cancellable sublease proceeds for the year ending January 31, 2022	5.0		5.0
Non-cancellable sublease proceeds for the year ending January 31, 2023	4.2		$ 4.2
Minimum
Commitments And Contingencies [Line Items]
Operating lease expiration year			2020
Capital lease initial term			3 years
Term of sublease arrangement			25 months
Maximum
Commitments And Contingencies [Line Items]
Operating lease expiration year			2029
Capital lease initial term			4 years
Term of sublease arrangement			55 months
November 2017 Facility | Letters of Credit | Secured Debt | Wells Fargo Bank
Commitments And Contingencies [Line Items]
Agreement entered date			Nov. 27, 2017
Letters of credit facility	$ 26.8		$ 26.8		$ 26.4
Line of credit facility, maximum borrowing capacity sublimit						$ 30.0