Summary of Significant Accounting Policies $ / shares in Units, $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2020 USD ($) $ / shares	Mar. 31, 2020 segment	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments | segment			1
Uninsured cash and cash equivalents		$ 8.5			$ 8.5		$ 186.1
Adoption of CECL	[1]				0.0
Provision for credit losses		(29.8)		$ 19.3	464.3	$ 49.2
CECL Impact on Net Income		$ 87.9			$ 328.2
CECL Impact on Net Income, Per Diluted Share | $ / shares		$ 4.92			$ 18.26
Restricted Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents		$ 388.1			$ 388.1		$ 326.7
New Consumer Loan Assignments [Member]
Summary Of Significant Accounting Policies [Line Items]
Provision for credit losses		114.1		0.0	426.2	0.0
Loans Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Adoption of CECL	[1]				2,463.6
Provision for credit losses		$ 0.0		$ 0.0	$ 0.0	$ 0.0

[1] Represents the gross-up of Loans receivable and allowance for credit losses on January 1, 2020 upon the adoption of CECL for the present value of the difference between contractual future net cash flows and expected future net cash flows discounted at the effective interest rate.