Summary Of Significant Accounting Policies (Schedule Of Other Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Other Income	$ 40.8	$ 40.2	$ 23.9
Vendor Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	12.9	15.0	7.8
Dealer Support Products And Services [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	10.8	9.8	8.0
Ancillary Product Profit Sharing Income [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	11.1	8.3	3.4
Dealer Enrollment Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	4.6	4.5	4.0
Other [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	$ 1.4	$ 2.6	$ 0.7