Leases - Lease cash flow information (Details) $ in Thousands	6 Months Ended
	Jul. 31, 2019 USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 16,167
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	$ 3,449
Weighted-average remaining lease term (years)	5 years 3 months 10 days
Weighted-average discount rate (as a percent)	6.46%