Leases - Narrative (Details) $ in Millions	12 Months Ended
	Jan. 31, 2019 USD ($)	Jan. 31, 2020 USD ($) agreement	Jan. 31, 2008 USD ($)
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term (years)		7 years
Weighted average discount rate (percent)		3.80%
Number of agreements not yet commenced | agreement		9
Value of leases not yet commenced		$ 88.7
Deferred gains on sale-leasebacks	$ 31.1	$ 0.0	$ 144.5
Minimum
Lessee, Lease, Description [Line Items]
Amortization period of sale-leaseback deferred gains (years)	15 years
Maximum
Lessee, Lease, Description [Line Items]
Amortization period of sale-leaseback deferred gains (years)	20 years