Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 24.7	$ 25.7
Restricted cash and cash equivalents	[1]	329.8	303.6
Restricted securities available for sale	[2]	59.8	58.6
Loans receivable, net	[1]	6,647.0	5,855.1
Revolving secured line of credit	[1]	52.2	171.9
Secured financing	[1]	3,292.2	3,100.9
Senior notes	[1]	990.9	556.3
Mortgage note	[1]	11.5	11.9
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	24.7	25.7
Restricted cash and cash equivalents	[1]	329.8	303.6
Restricted securities available for sale	[2]	47.9	47.9
Senior notes	[1]	990.9	556.3
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]	11.9	10.7
Revolving secured line of credit	[1]	52.2	171.9
Secured financing	[1]	3,292.2	3,100.9
Mortgage note	[1]	11.5	11.9
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net	[1]	$ 6,647.0	$ 5,855.1

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

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