Recently Issued Accounting Standards (Adoption of New Accounting Standard - Balance Sheet) (Details) - USD ($) $ in Millions	Jul. 31, 2019	Feb. 01, 2019	Jan. 31, 2019
ASSETS
Prepaid expenses and other current assets	$ 176.8	$ 186.2	$ 192.1
Total current assets	1,515.5	1,614.1	1,620.0
Operating lease right-of-use assets	298.8	283.4
Total assets	4,872.7	5,006.7	4,729.2
Current liabilities:
Other accrued liabilities	114.4	137.4	142.3
Operating lease liabilities	58.9	54.1
Long-term operating lease liabilities	258.1	245.9
Other liabilities	116.0	104.9	121.8
Accumulated deficit	$ (2,224.3)	(2,148.1)	$ (2,147.4)
Accounting Standards Update 2016-02
ASSETS
Prepaid expenses and other current assets		(5.9)
Total current assets		(5.9)
Operating lease right-of-use assets		283.4
Total assets		277.5
Current liabilities:
Other accrued liabilities		(4.9)
Operating lease liabilities		54.1
Long-term operating lease liabilities		245.9
Other liabilities		(16.9)
Accumulated deficit		$ (0.7)