Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 8.9	$ 187.4
Restricted cash and cash equivalents	[1]	391.9	330.3
Restricted securities available for sale	[2]	66.8	59.3
Loans receivable, net	[1]	7,263.0	6,777.2
Revolving secured line of credit	[1]	125.7	0.0
Secured financing	[1]	3,762.0	3,397.5
Senior notes	[1]	808.1	1,257.6
Mortgage note	[1]	10.7	11.3
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	8.9	187.4
Restricted cash and cash equivalents	[1]	391.9	330.3
Restricted securities available for sale	[2]	53.8	47.5
Senior notes	[1]	808.1	1,257.6
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]	13.0	11.8
Revolving secured line of credit	[1]	125.7	0.0
Secured financing	[1]	3,762.0	3,397.5
Mortgage note	[1]	10.7	11.3
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net	[1]	$ 7,263.0	$ 6,777.2

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

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