Other Income (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Other Income	$ 83.4	$ 53.1	$ 49.6
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	14.5
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	68.9
Ancillary Product Profit Sharing [Member]
Disaggregation of Revenue [Line Items]
Other Income	60.6	40.2	33.5
Ancillary Product Profit Sharing [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Ancillary Product Profit Sharing [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	60.6
Remarketing Fees [Member]
Disaggregation of Revenue [Line Items]
Other Income	13.4	7.8	7.1
Remarketing Fees [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	13.4
Remarketing Fees [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Dealer Enrollment Fees [Member]
Disaggregation of Revenue [Line Items]
Other Income	1.7	1.9	3.0
Dealer Enrollment Fees [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Dealer Enrollment Fees [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	1.7
Dealer Support Products And Services [Member]
Disaggregation of Revenue [Line Items]
Other Income	1.2	1.3	1.9
Dealer Support Products And Services [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	1.2
Dealer Support Products And Services [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Interest Income [Member]
Disaggregation of Revenue [Line Items]
Other Income	6.6	1.2	2.9
Interest Income [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Interest Income [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	6.6
Other [Member]
Disaggregation of Revenue [Line Items]
Other Income	(0.1)	$ 0.7	$ 1.2
Other [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	(0.1)
Other [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Third Party Providers [Member]
Disaggregation of Revenue [Line Items]
Other Income	67.1
Third Party Providers [Member] | Ancillary Product Profit Sharing [Member]
Disaggregation of Revenue [Line Items]
Other Income	60.6
Third Party Providers [Member] | Remarketing Fees [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Third Party Providers [Member] | Dealer Enrollment Fees [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Third Party Providers [Member] | Dealer Support Products And Services [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Third Party Providers [Member] | Interest Income [Member]
Disaggregation of Revenue [Line Items]
Other Income	6.6
Third Party Providers [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Other Income	(0.1)
Dealers [Member]
Disaggregation of Revenue [Line Items]
Other Income	16.3
Dealers [Member] | Ancillary Product Profit Sharing [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Dealers [Member] | Remarketing Fees [Member]
Disaggregation of Revenue [Line Items]
Other Income	13.4
Dealers [Member] | Dealer Enrollment Fees [Member]
Disaggregation of Revenue [Line Items]
Other Income	1.7
Dealers [Member] | Dealer Support Products And Services [Member]
Disaggregation of Revenue [Line Items]
Other Income	1.2
Dealers [Member] | Interest Income [Member]
Disaggregation of Revenue [Line Items]
Other Income	0.0
Dealers [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Other Income	$ 0.0