Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Jan. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Noncancelable operating lease expiration, start year			2018
Noncancelable operating lease expiration, end year			2023
Noncancelable capital lease expiration, start year			2018
Noncancelable capital lease expiration, end year			2023
Operating leases, rent expense	$ 1.6	$ 1.1	$ 3.1	$ 2.3
Purchase commitment with contract manufacturer	$ 24.4		$ 24.4		$ 13.5