Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Assets
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
Liabilities
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
Carrying Amount [Member]
Assets
Cash and cash equivalents		8.9	187.4
Restricted cash and cash equivalents		391.9	330.3
Restricted securities available for sale		66.8	59.3
Loans receivable, net		6,865.2	6,685.2
Liabilities
Revolving secured line of credit		125.7	0.0
Secured financing		3,692.8	3,339.7
Senior notes		790.1	1,187.8
Mortgage note		10.7	11.3
Estimated Fair Value [Member]
Assets
Cash and cash equivalents		8.9	187.4
Restricted cash and cash equivalents		391.9	330.3
Restricted securities available for sale		66.8	59.3
Loans receivable, net		7,263.0	6,777.2
Liabilities
Revolving secured line of credit		125.7	0.0
Secured financing		3,762.0	3,397.5
Senior notes		808.1	1,257.6
Mortgage note		$ 10.7	$ 11.3

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

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