Summary of Significant Accounting Policies - New Accounting Standards (Details) - USD ($) $ in Millions	Jan. 31, 2020	Feb. 01, 2019	Jan. 31, 2019	Feb. 01, 2018	Jan. 31, 2008
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	$ 1,211.2
Deferred gains on sale-leasebacks	0.0		$ (31.1)		$ (144.5)
Deferred tax asset on deferred gains on sale-leasebacks	0.0		(13.1)
Retained earnings	$ 2,207.6		2,045.6
Cumulative effect adjustment from adoption of new accounting standards		$ 21.8		$ 3.9
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability		1,200.0
Deferred gains on sale-leasebacks			31.1
Deferred tax asset on deferred gains on sale-leasebacks			$ 9.5
Accounting Standards Update 2016-02, Sale Leaseback Transaction, Deferred Gain, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		31.1
Accounting Standards Update 2016-02, Deferred Tax Assets, Deferred Gain On Sale Leaseback Transaction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		(9.5)
Accumulated Other Comprehensive Loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment from adoption of new accounting standards		(26.0)		1.8
Accumulated Other Comprehensive Loss | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment from adoption of new accounting standards		26.2
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment from adoption of new accounting standards		47.8		$ 2.1
Retained Earnings | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment from adoption of new accounting standards		$ 26.2