Loans Receivable - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecast changes	$ 24.4	$ (206.5)	$ 13.0	$ (182.1)	$ 29.7
Certain Loans Acquired In Transfer Accounted For As Loans Accretable Yield Reclassifications From Nonaccretable Difference Forecast Changes, By Percentage				2.30%
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecast changes	(0.1)		3.4	$ (76.0)	3.9
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecast changes	24.5		$ 9.6	$ (106.1)	$ 25.8
Forecast Changes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecast changes	(44.3)
COVID-19 Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecast changes	$ (162.2)