Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		$ 4.9	$ 14.6
Restricted cash and cash equivalents		273.6	224.7
Restricted securities available for sale	[1]	46.1	45.3
Loans receivable, net		4,536.9	3,955.9
Revolving secured line of credit		130.5	0.0
Secured financing		2,348.5	2,072.0
Senior notes		569.0	560.5
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		4.9	14.6
Restricted cash and cash equivalents		273.6	224.7
Restricted securities available for sale	[1]	36.9	37.1
Revolving secured line of credit		130.5
Senior notes		569.0	560.5
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted securities available for sale	[1]	9.2	8.2
Revolving secured line of credit		0.0	0.0
Secured financing		2,348.5	2,072.0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, net		$ 4,536.9	$ 3,955.9

[1] Measured and recorded at fair value on a recurring basis.