Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	$ 19.7	$ 25.7
Restricted cash and cash equivalents	[1]	328.8	303.6
Restricted securities available for sale	[2]	61.5	58.6
Loans receivable, net	[1]	6,466.8	5,855.1
Revolving secured line of credit	[1]	38.4	171.9
Secured financing	[1]	3,275.6	3,100.9
Senior notes	[1]	985.2	556.3
Mortgage note	[1]	11.6	11.9
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	[1]	19.7	25.7
Restricted cash and cash equivalents	[1]	328.8	303.6
Restricted securities available for sale	[2]	49.4	47.9
Senior notes	[1]	985.2	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]	12.1	10.7
Revolving secured line of credit	[1]	38.4	171.9
Secured financing	[1]	3,275.6	3,100.9
Mortgage note	[1]	11.6	11.9
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net	[1]	$ 6,466.8	$ 5,855.1

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

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