Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 8.4	$ 13.2
Restricted cash and cash equivalents	[1]	559.2	457.7
Debt Securities, Available-for-sale	[2]	99.9	93.2
Loans receivable, net	[1]	8,215.3	7,759.1
Revolving secured lines of credit	[1]	169.5	79.2
Secured financing	[1]	4,304.6	4,025.9
Senior notes	[1]	1,045.8	1,039.8
Mortgage note	[1]	8.3	8.4
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	8.4	13.2
Restricted cash and cash equivalents	[1]	559.2	457.7
Debt Securities, Available-for-sale	[2]	79.1	75.1
Secured financing	[1]	3,444.5	3,225.8
Senior notes	[1]	1,045.8	1,039.8
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]	20.8	18.1
Revolving secured lines of credit	[1]	169.5	79.2
Secured financing	[1]	860.1	800.1
Mortgage note	[1]	8.3	8.4
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net	[1]	$ 8,215.3	$ 7,759.1

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

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