Recently Issued Accounting Standards (Adoption of New Accounting Standard - Balance Sheet) (Details) - USD ($) $ in Millions	Oct. 31, 2019	Feb. 01, 2019	Jan. 31, 2019
ASSETS
Prepaid expenses and other current assets	$ 162.0	$ 186.2	$ 192.1
Total current assets	1,706.8	1,614.1	1,620.0
Operating lease right-of-use assets	281.7	283.4
Total assets	5,036.6	5,006.7	4,729.2
Current liabilities:
Other accrued liabilities	129.7	137.4	142.3
Operating lease liabilities	64.0	54.1
Long-term operating lease liabilities	239.8	245.9
Other liabilities	116.6	104.9	121.8
Accumulated deficit	$ (2,240.3)	(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)