Store Closures (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) store	Dec. 31, 2017 USD ($) store
Restructuring and Related Cost, Expected Cost
Number of underperforming store closures | store	60
Restructuring charge incurred | $	$ 199.0
Forecast
Restructuring and Related Cost, Expected Cost
Number of underperforming store closures | store		70
Additional Restructuring charges expected to be incurred | $		$ 20.0