Loans Receivable (Schedule of Consumer Loans Performance) - USD ($) $ in Millions	Sep. 30, 2020		Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	$ 10,176.1	[1],[2]		$ 7,221.2
Allowance for credit losses	(3,310.9)			(536.0)
Loans receivable, net	6,865.2		$ 6,749.8	6,685.2	$ 6,563.7	$ 6,384.0	$ 5,763.3
Loan Pool Performance Meets Or Exceeds Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				3,598.2
Allowance for credit losses				0.0
Loans receivable, net				3,598.2
Loan Pool Performance Less Than Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				3,623.0
Allowance for credit losses				(536.0)
Loans receivable, net				3,087.0
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	5,857.7	[1]		4,623.3
Allowance for credit losses	(1,634.8)			(428.0)
Loans receivable, net	4,222.9		4,187.2	4,195.3	4,150.0	4,072.0	3,762.9
Dealer Loans [Member] | Loan Pool Performance Meets Or Exceeds Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				1,591.3
Allowance for credit losses				0.0
Loans receivable, net				1,591.3
Dealer Loans [Member] | Loan Pool Performance Less Than Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				3,032.0
Allowance for credit losses				(428.0)
Loans receivable, net				2,604.0
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	4,318.4	[2]		2,597.9
Allowance for credit losses	(1,676.1)			(108.0)
Loans receivable, net	$ 2,642.3		$ 2,562.6	2,489.9	$ 2,413.7	$ 2,312.0	$ 2,000.4
Purchased Loans [Member] | Loan Pool Performance Meets Or Exceeds Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				2,006.9
Allowance for credit losses				0.0
Loans receivable, net				2,006.9
Purchased Loans [Member] | Loan Pool Performance Less Than Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				591.0
Allowance for credit losses				(108.0)
Loans receivable, net				$ 483.0

[1] As Consumer Loans are aggregated by Dealer for purposes of recognizing revenue and evaluating impairment, the Dealer Loan amount was estimated by allocating the balance of each Dealer Loan to the underlying Consumer Loans based on the forecasted future collections of each Consumer Loan.

[2] As certain Consumer Loans are aggregated by Dealer or month of purchase for purposes of recognizing revenue and evaluating impairment, the Purchased Loan amount was estimated by allocating the balance of certain Purchased Loans to the underlying Consumer Loans based on the forecasted future collections of each Consumer Loan.