Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	[1]	$ 25.7	$ 187.4
Restricted cash and cash equivalents	[1]	408.1	330.3
Restricted securities available for sale	[2]	63.2	59.3
Loans receivable, net	[1]	7,044.3	6,777.2
Liabilities
Revolving secured line of credit	[1]	79.9	0.0
Secured financing	[1]	3,915.7	3,397.5
Senior notes	[1]	738.6	1,257.6
Mortgage note	[1]	11.1	11.3
Carrying Amount [Member]
Assets
Cash and cash equivalents		25.7	187.4
Restricted cash and cash equivalents		408.1	330.3
Restricted securities available for sale		63.2	59.3
Loans receivable, net		6,618.5	6,685.2
Liabilities
Revolving secured line of credit		79.9	0.0
Secured financing		3,957.6	3,339.7
Senior notes		789.2	1,187.8
Mortgage note		11.1	11.3
Estimated Fair Value [Member]
Assets
Cash and cash equivalents		25.7	187.4
Restricted cash and cash equivalents		408.1	330.3
Restricted securities available for sale		63.2	59.3
Loans receivable, net		7,044.3	6,777.2
Liabilities
Revolving secured line of credit		79.9	0.0
Secured financing		3,915.7	3,397.5
Senior notes		738.6	1,257.6
Mortgage note		$ 11.1	$ 11.3

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

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