Divestitures (Details) $ in Millions	3 Months Ended
	Sep. 30, 2017 USD ($) store	Jun. 30, 2017 USD ($) store	Mar. 31, 2017 USD ($) store	Sep. 30, 2016 USD ($) store	Jun. 30, 2016 USD ($) store	Mar. 31, 2016 USD ($) store
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal | $	$ 9.3	$ 14.8	$ 4.3	$ 11.8	$ 11.5	$ 6.2
Import Stores Divested [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of stores divested	1	1	1	1	6	2
Domestic Stores Divested [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of stores divested	1			1	1