Summary Of Significant Accounting Policies (Schedule Of Other Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Other Income	$ 51.9	$ 46.6	$ 40.8
Ancillary Product Profit Sharing [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	15.5	11.9	11.1
GPS-SID Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	13.5	16.4	12.8
Remarketing Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	9.2	6.9	6.2
Dealer Enrollment Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	5.0	4.8	4.6
Dealer Support Products And Services [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	4.7	4.9	4.6
Other [Member]
Summary Of Significant Accounting Policies [Line Items]
Other Income	$ 4.0	$ 1.7	$ 1.5