Acquisitions (Details) $ in Millions		12 Months Ended
	Feb. 10, 2016 stores	Dec. 31, 2015 USD ($) stores	Dec. 31, 2014 USD ($) stores	Dec. 31, 2013 USD ($) stores
Subsequent Event [Line Items]
Number of stores purchased		22	5	5
Amounts incurred related to acquisitions | $		$ 321.5	$ 205.2	$ 87.9
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of stores purchased	12