Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) - USD ($) $ in Millions		Mar. 31, 2022	Dec. 31, 2021
Assets
Cash and cash equivalents	[1]	$ 17.6	$ 23.3
Restricted cash and cash equivalents	[1]	481.1	410.9
Debt Securities, Available-for-sale, Restricted		62.4	62.1
Loans receivable, net	[1]	6,543.7	6,580.4
Liabilities
Revolving secured line of credit	[1]	104.7	2.6
Secured financing	[1]	3,775.8	3,832.1
Senior notes	[1]	812.7	825.8
Mortgage note	[1]	9.4	9.7
Carrying Amount [Member]
Assets
Cash and cash equivalents		17.6	23.3
Restricted cash and cash equivalents		481.1	410.9
Debt Securities, Available-for-sale, Restricted		62.4	62.1
Loans receivable, net		6,327.2	6,336.3
Liabilities
Revolving secured line of credit		104.7	2.6
Secured financing		3,832.4	3,811.5
Senior notes		792.5	792.5
Mortgage note		9.4	9.7
Estimated Fair Value [Member]
Assets
Cash and cash equivalents		17.6	23.3
Restricted cash and cash equivalents		481.1	410.9
Debt Securities, Available-for-sale, Restricted		62.4	62.1
Loans receivable, net		6,543.7	6,580.4
Liabilities
Revolving secured line of credit		104.7	2.6
Secured financing		3,775.8	3,832.1
Senior notes		812.7	825.8
Mortgage note		$ 9.4	$ 9.7

[1] Measured at amortized cost with fair value disclosed.