Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Assets
Cash and cash equivalents	[1]	$ 8.4	$ 13.2
Restricted cash and cash equivalents	[1]	559.2	457.7
Debt Securities, Available-for-sale, Restricted		99.9	93.2
Loans receivable, net	[1]	8,215.3	7,759.1
Liabilities
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
Carrying Amount [Member]
Assets
Cash and cash equivalents		8.4	13.2
Restricted cash and cash equivalents		559.2	457.7
Debt Securities, Available-for-sale, Restricted		99.9	93.2
Loans receivable, net		7,345.6	6,955.3
Liabilities
Revolving secured lines of credit		169.5	79.2
Secured financing		4,444.1	3,990.9
Senior notes		989.6	989.0
Mortgage note		8.3	8.4
Estimated Fair Value [Member]
Assets
Cash and cash equivalents		8.4	13.2
Restricted cash and cash equivalents		559.2	457.7
Debt Securities, Available-for-sale, Restricted		99.9	93.2
Loans receivable, net		8,215.3	7,759.1
Liabilities
Revolving secured lines of credit		169.5	79.2
Secured financing		4,304.6	4,025.9
Senior notes		1,045.8	1,039.8
Mortgage note		$ 8.3	$ 8.4

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