Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Assets
Cash and cash equivalents	[1]	$ 3.1	$ 7.7
Restricted cash and cash equivalents	[1]	435.1	410.0
Debt Securities, Available-for-sale, Restricted		86.2	72.3
Loans receivable, net	[1]	7,529.4	6,767.9
Liabilities
Revolving secured lines of credit	[1]	102.1	30.9
Secured financing	[1]	4,015.3	3,581.9
Senior notes	[1]	745.0	759.0
Mortgage note	[1]	8.5	8.9
Carrying Amount [Member]
Assets
Cash and cash equivalents		3.1	7.7
Restricted cash and cash equivalents		435.1	410.0
Debt Securities, Available-for-sale, Restricted		86.2	72.3
Loans receivable, net		6,780.5	6,297.7
Liabilities
Revolving secured lines of credit		102.1	30.9
Secured financing		4,034.2	3,756.4
Senior notes		796.0	794.5
Mortgage note		8.5	8.9
Estimated Fair Value [Member]
Assets
Cash and cash equivalents		3.1	7.7
Restricted cash and cash equivalents		435.1	410.0
Debt Securities, Available-for-sale, Restricted		86.2	72.3
Loans receivable, net		7,529.4	6,767.9
Liabilities
Revolving secured lines of credit		102.1	30.9
Secured financing		4,015.3	3,581.9
Senior notes		745.0	759.0
Mortgage note		$ 8.5	$ 8.9

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