Accounts receivable, net - Credit Quality Indicator and Age Analysis (Details) - USD ($) $ in Millions	Apr. 29, 2017	Jan. 28, 2017	Apr. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 1,810.7	$ 1,952.0	$ 1,771.1
Valuation allowance	$ (126.9)	$ (138.7)	$ (116.8)
Gross	100.00%	100.00%	100.00%
Valuation allowance	7.00%	7.10%	6.60%
Current, aged 0 – 30 days | Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 1,445.9	$ 1,538.2	$ 1,427.5
Valuation allowance	$ (44.5)	$ (47.2)	$ (43.4)
Gross	79.80%	78.80%	80.60%
Valuation allowance	3.10%	3.10%	3.00%
Past due, aged 31 – 60 days | Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 251.9	$ 282.0	$ 240.9
Valuation allowance	$ (8.3)	$ (9.0)	$ (7.9)
Gross	13.90%	14.50%	13.60%
Valuation allowance	3.30%	3.20%	3.30%
Past due, aged 61 – 90 days | Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 40.9	$ 51.6	$ 39.2
Valuation allowance	$ (2.1)	$ (2.3)	$ (2.0)
Gross	2.30%	2.60%	2.20%
Valuation allowance	5.10%	4.50%	5.10%
Past due, aged more than 90 days | Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross	$ 72.0	$ 80.2	$ 63.5
Valuation allowance	$ (72.0)	$ (80.2)	$ (63.5)
Gross	4.00%	4.10%	3.60%
Valuation allowance	100.00%	100.00%	100.00%