Summary Of Significant Accounting Policies (Schedule Of Other Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]
Other income	$ 23.9	$ 24.6	$ 21.4
Ancillary Product Profit Sharing Income [Member]
Summary Of Significant Accounting Policies [Line Items]
Other income	3.4	7.8	4.1
Dealer Support Products And Services [Member]
Summary Of Significant Accounting Policies [Line Items]
Other income	8.0	7.3	7.2
Vendor Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other income	7.8	4.2	5.8
Dealer Enrollment Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other income	4.0	3.5	2.7
Other [Member]
Summary Of Significant Accounting Policies [Line Items]
Other income	$ 0.7	$ 1.8	$ 1.6