Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 3.1	$ 7.7
Restricted cash and cash equivalents	[1]	435.1	410.0
Debt Securities, Available-for-sale	[2]	86.2	72.3
Loans receivable, net	[1]	7,529.4	6,767.9
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
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	3.1	7.7
Restricted cash and cash equivalents	[1]	435.1	410.0
Debt Securities, Available-for-sale	[2]	69.6	58.7
Secured financing	[1]	3,014.2	2,781.8
Senior notes	[1]	745.0	759.0
Mortgage note	[1]	0.0	0.0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[2]	16.6	13.6
Revolving secured lines of credit	[1]	102.1	30.9
Secured financing	[1]	1,001.1	800.1
Mortgage note	[1]	8.5	8.9
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net	[1]	$ 7,529.4	$ 6,767.9

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

[2] Measured at fair value on a recurring basis.