Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Balance Sheet Grouping, Financial Statement Captions
Carrying value	$ 349.8	$ 283.5
NSM Holding Co LLC
Balance Sheet Grouping, Financial Statement Captions
Carrying value	268.4	219.2
NSM Holding Co LLC | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	267.0	217.4
NSM Holding Co LLC | Carrying Value | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	267.0	217.4
NSM Holding Co LLC | Estimate of Fair Value Measurement | NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	272.2	221.2
NSM Holding Co LLC | Estimate of Fair Value Measurement | Other NSM
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	1.6	1.7
Kudu | Kudu Debt [Member]
Balance Sheet Grouping, Financial Statement Captions
Carrying value	70.8	53.6
Kudu | Estimate of Fair Value Measurement | Kudu Debt [Member]
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	72.8	53.6
Other Operations | Carrying Value
Balance Sheet Grouping, Financial Statement Captions
Carrying value		10.7
Other Operations | Estimate of Fair Value Measurement
Balance Sheet Grouping, Financial Statement Captions
Debt Instrument, Fair Value Disclosure	9.5	11.3
Term Loan | NSM Holding Co LLC | Other NSM
Balance Sheet Grouping, Financial Statement Captions
Carrying value	$ 1.4	$ 1.8