Accounts receivable, net - Credit Quality Indicator and Age Analysis (Details) - USD ($) $ in Millions	Aug. 01, 2015	Jan. 31, 2015	Aug. 02, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 1,599.1	$ 1,666.0	$ 1,404.0
Valuation allowance	$ (116.0)	$ (113.1)	$ (98.9)
Gross	100.00%	100.00%	100.00%
Valuation allowance	7.30%	6.80%	7.00%
Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	95.70%	96.20%	96.00%
Valuation allowance	3.10%	3.10%	3.10%
Performing Financing Receivable | Period One | 0 to 30 Days Aged Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 1,252.4	$ 1,332.2	$ 1,110.6
Valuation allowance	(38.1)	(41.1)	(34.0)
Performing Financing Receivable | Period Two | 31 to 90 Days Aged Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	278.4	271.1	236.8
Valuation allowance	$ (9.6)	$ (9.3)	$ (8.3)
Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	4.30%	3.80%	4.00%
Valuation allowance	100.00%	100.00%	100.00%
Nonperforming Financing Receivable | Period Two | More Than 90 Days Aged Non Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 68.3	$ 62.7	$ 56.6
Valuation allowance	$ (68.3)	$ (62.7)	$ (56.6)