Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Balance Sheet Grouping, Financial Statement Captions
Carrying value	$ 359.4	$ 283.5
Other NSM debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value		1.8
Fair Value | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	276.1	221.2
Fair Value | Other NSM debt
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	1.6	1.7
Fair Value | Kudu Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	74.4	53.6
Fair Value | Other Operations debt
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	18.5	11.3
Carrying Value | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	268.8	217.4
Carrying Value | Other NSM debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value	1.4	1.8
Carrying Value | Kudu Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	71.0	53.6
Carrying Value | Other Operations debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value	$ 18.2	$ 10.7