Goodwill and intangibles - Composition of Finite-Lived Intangibles (Details) - USD ($) $ in Millions	Apr. 30, 2016	Jan. 30, 2016	May. 02, 2015
Definite-lived intangible assets:
Gross carrying amount	$ 49.8	$ 48.4	$ 50.1
Accumulated amortization	(26.8)	(22.8)	(12.9)
Net carrying amount	23.0	25.6	37.2
Intangible assets, gross	457.2	450.6	458.8
Total intangible assets, net	430.4	427.8	445.9
Definite-lived intangible liabilities:
Gross carrying amount	(114.4)	(113.3)	(114.7)
Accumulated amortization	57.1	51.8	32.3
Total	(57.3)	(61.5)	(82.4)
Unfavorable leases
Definite-lived intangible liabilities:
Gross carrying amount	(48.8)	(47.7)	(49.1)
Accumulated amortization	27.7	23.7	13.3
Total	(21.1)	(24.0)	(35.8)
Unfavorable contracts
Definite-lived intangible liabilities:
Gross carrying amount	(65.6)	(65.6)	(65.6)
Accumulated amortization	29.4	28.1	19.0
Total	(36.2)	(37.5)	(46.6)
Trade names
Definite-lived intangible assets:
Gross carrying amount	1.5	1.4	1.5
Accumulated amortization	(0.6)	(0.5)	(0.3)
Net carrying amount	0.9	0.9	1.2
Favorable leases
Definite-lived intangible assets:
Gross carrying amount	48.3	47.0	48.6
Accumulated amortization	(26.2)	(22.3)	(12.6)
Net carrying amount	22.1	24.7	36.0
Trade names
Definite-lived intangible assets:
Indefinite-lived trade names	$ 407.4	$ 402.2	$ 408.7