Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Concentration Risk [Line Items]
Cost of merchandise sold	$ 6,094.9	$ 5,821.6	$ 5,369.9
Operating lease right-of-use assets	117.5
Operating lease liabilities	$ 124.8
Accounting Standards Update 2016-02 [Member]
Concentration Risk [Line Items]
Operating lease right-of-use assets				$ 91.8
Operating lease liabilities				$ 98.1
Minimum
Concentration Risk [Line Items]
Amortization period	3 years
Maximum
Concentration Risk [Line Items]
Amortization period	20 years
Outgoing Freight Expenses [Member]
Concentration Risk [Line Items]
Cost of merchandise sold	$ 68.5	$ 65.7	$ 57.7
Sales revenue | Services | Maximum
Concentration Risk [Line Items]
Concentration percentage	1.00%
Freight Expenses As Selling, General And Administrative Expenses [Member] | Outgoing Freight Expenses [Member]
Concentration Risk [Line Items]
Concentration percentage	95.00%