Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 45.7	$ 16.0
Restricted cash and cash equivalents	[1]	538.5	380.2
Restricted securities available for sale	[2]	68.1	66.1
Loans receivable, net	[1]	7,254.1	7,216.4
Revolving secured line of credit	[1]	0.0	95.9
Secured financing	[1]	3,993.6	3,793.9
Senior notes	[1]	829.5	842.0
Mortgage note	[1]	10.3	10.5
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	45.7	16.0
Restricted cash and cash equivalents	[1]	538.5	380.2
Restricted securities available for sale	[2]	55.0	52.8
Senior notes	[1]	829.5	842.0
Mortgage note	[1]	0.0	0.0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted securities available for sale	[2]	13.1	13.3
Revolving secured line of credit	[1]	0.0	95.9
Secured financing	[1]	3,993.6	3,793.9
Mortgage note	[1]	10.3	10.5
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net	[1]	$ 7,254.1	$ 7,216.4

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

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