Goodwill and intangibles - Composition of Finite-Lived Intangibles (Details) - USD ($) $ in Millions	Oct. 29, 2016	Jan. 30, 2016	Oct. 31, 2015
Definite-lived intangible assets:
Gross carrying amount	$ 48.9	$ 48.4	$ 49.1
Accumulated amortization	(33.3)	(22.8)	(19.6)
Net carrying amount	15.6	25.6	29.5
Intangible assets, gross	453.1	450.6	453.9
Total intangible assets, net	419.8	427.8	434.3
Definite-lived intangible liabilities:
Gross carrying amount	(113.7)	(113.3)	(113.9)
Accumulated amortization	66.8	51.8	48.0
Total	(46.9)	(61.5)	(65.9)
Unfavorable leases
Definite-lived intangible liabilities:
Gross carrying amount	(48.1)	(47.7)	(48.3)
Accumulated amortization	34.7	23.7	20.4
Total	(13.4)	(24.0)	(27.9)
Unfavorable contracts
Definite-lived intangible liabilities:
Gross carrying amount	(65.6)	(65.6)	(65.6)
Accumulated amortization	32.1	28.1	27.6
Total	(33.5)	(37.5)	(38.0)
Trade names
Definite-lived intangible assets:
Gross carrying amount	1.4	1.4	1.5
Accumulated amortization	(0.7)	(0.5)	(0.4)
Net carrying amount	0.7	0.9	1.1
Favorable leases
Definite-lived intangible assets:
Gross carrying amount	47.5	47.0	47.6
Accumulated amortization	(32.6)	(22.3)	(19.2)
Net carrying amount	14.9	24.7	28.4
Trade names
Definite-lived intangible assets:
Indefinite-lived trade names	$ 404.2	$ 402.2	$ 404.8