Leases - Lease assets and liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2019	Feb. 01, 2019
Assets and Liabilities, Lessee [Abstract]
Operating lease assets	$ 320,169	$ 341,200
Classification of operating lease assets	us-gaap:OperatingLeaseRightOfUseAsset
Total lease assets	$ 320,169
Current operating lease liabilities	$ 74,761
Classification current operating lease liabilities	us-gaap:OperatingLeaseLiabilityCurrent
Noncurrent operating liabilities	$ 286,663
Classification of noncurrent operating liabilities	us-gaap:OperatingLeaseLiabilityNoncurrent
Total lease liabilities	$ 361,424	$ 384,500