Debt - Debt Outstanding (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Apr. 07, 2020	Dec. 31, 2018	May 18, 2018	May 11, 2018
Debt Instrument
Debt	$ 376,400,000	$ 283,500,000
Weighted average interest rate	7.00%	7.00%
NSM Bank Facility
Debt Instrument
Effective yield (as a percent)	8.40%	8.10%
NSM
Debt Instrument
Debt instrument at face value						$ 100,000,000.0
Debt	$ 272,600,000	$ 219,200,000
NSM | NSM Bank Facility
Debt Instrument
Debt instrument at face value	277,400,000
Debt	277,400,000	221,300,000		$ 180,400,000
Kudu | Kudu Debt
Debt Instrument
Debt	86,300,000	53,600,000
Other Operations | Other
Debt Instrument
Debt	17,500,000	10,700,000
Term Loan | NSM | NSM Bank Facility
Debt Instrument
Debt instrument at face value	277,400,000	221,300,000	$ 276,400,000		$ 51,000,000.0
Unamortized Debt Issuance Expense	(6,100,000)	(3,900,000)
Debt	$ 271,300,000	$ 217,400,000
Effective yield (as a percent)	7.50%	7.50%
Term Loan | NSM | Other NSM
Debt Instrument
Debt instrument at face value	$ 1,300,000
Debt	$ 1,300,000	$ 1,800,000
Effective yield (as a percent)	2.50%	3.00%
Term Loan | Kudu | Kudu Debt
Debt Instrument
Unamortized Debt Issuance Expense	$ (2,900,000)	$ (3,400,000)
Effective yield (as a percent)	8.30%	8.30%
Term Loan | Kudu | Kudu Debt
Debt Instrument
Debt instrument at face value	$ 89,200,000	$ 57,000,000.0
Term Loan | Other Operations | Other Debt
Debt Instrument
Effective yield (as a percent)	7.40%	8.30%
Term Loan | Other Operations | Other
Debt Instrument
Debt instrument at face value	$ 18,000,000.0	$ 11,100,000
Unamortized Debt Issuance Expense	$ (500,000)	(400,000)
Debt		$ 10,700,000