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Derivatives - NSM Interest Rate Swap (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		8 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Jun. 15, 2018
Derivative [Line Items]
Debt	$ 230.5		$ 230.5		$ 192.7
NSM Holding Co LLC
Derivative [Line Items]
Debt	219.7		219.7		178.5
NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt	218.0		218.0		176.6
Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt	$ 222.3		$ 222.3
Interest Rate Swap \| NSM Holding Co LLC
Derivative [Line Items]
Derivative, fixed interest rate						2.97%
Derivative, variable interest rate	2.43%		2.43%
Interest expense, net	$ 0.2	$ 0.1	$ 0.4	$ 0.1
Derivative, fair value, net	7.0		7.0		$ 2.7
Change in fair value of derivative	$ (2.4)	$ (1.1)	$ (4.3)	$ (1.1)
Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Total commitment under revolving credit facility						$ 151.0
Derivative, fixed interest rate	2.97%		2.97%
Debt	$ 149.5		$ 149.5
Debt, weighted average interest rate, all-in	7.30%		7.30%
Margin over London Interbank Offered Rate (LIBOR) \| Minimum \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Basis spread on variable rate	4.25%				4.25%
Margin over London Interbank Offered Rate (LIBOR) \| Maximum \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Basis spread on variable rate	4.75%				4.75%
Margin over Prime Rate \| Minimum \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Basis spread on variable rate	3.25%				3.25%
Margin over Prime Rate \| Maximum \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Basis spread on variable rate	3.75%				3.75%
Designated as Hedging Instrument \| Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt	$ 149.5		$ 149.5
Debt, weighted average interest rate, all-in	7.47%		7.47%