Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Face (par) amount of debt instrument at time of issuance.

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Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

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The premium (cost) of a hedge, expensed during the period.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fixed interest rate related to the interest rate derivative.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Variable interest rate in effect as of the balance sheet date related to the interest rate derivative.

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The net amount of operating interest income (expense).

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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LIBOR rate

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Derivatives - NSM Interest Rate Swap and Cap (Details) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 04, 2020	Apr. 07, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 15, 2018	May 11, 2018
Derivative [Line Items]
Total commitment under revolving credit facility		$ 234,000,000.0					$ 291.4
Debt	$ 349,800,000			$ 349,800,000				$ 283,500,000
NSM Bank Facility
Derivative [Line Items]
Debt Instrument, Face Amount												$ 100,000,000.0
NSM Holding Co LLC
Derivative [Line Items]
Debt	268,400,000			268,400,000				219,200,000
NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt	$ 267,000,000.0			$ 267,000,000.0				$ 217,400,000
Debt, weighted average interest rate, all-in	7.21%			7.21%				6.60%
Debt Instrument, Face Amount	$ 273,400,000	220,700,000	$ 222,300,000	$ 273,400,000	$ 222,300,000			$ 221,300,000	$ 186,400,000	$ 180,400,000
Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt Instrument, Face Amount	$ 273,400,000	$ 224,000,000.0		$ 273,400,000			276,400,000	221,300,000
Interest Rate Swap \| NSM Holding Co LLC
Derivative [Line Items]
Derivative, fixed interest rate											2.97%
Derivative, variable interest rate	0.17%			0.17%
Interest expense, net	$ 700,000		200,000	$ 1,200,000	400,000
Derivative, fair value, net			9,400,000		9,400,000			$ 6,600,000
Change in fair value of derivative	400,000		$ (2,400,000)	(2,800,000)	$ (4,300,000)
Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Total commitment under revolving credit facility											$ 151,000,000.0
Derivative, fixed interest rate		2.97%
Debt	$ 148,400,000			$ 148,400,000
Debt, weighted average interest rate, all-in	6.78%			6.78%
Interest Rate Cap \| NSM Holding Co LLC
Derivative [Line Items]
Derivative, Cost of Hedge				$ 100,000
Derivative, Cap Interest Rate	1.25%			1.25%
LIBOR rate	0.14%			0.14%
Derivative, fair value, net	$ 100,000			$ 100,000
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%		5.50%
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%		6.00%
Designated as Hedging Instrument \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt, weighted average interest rate, all-in	6.67%			6.67%
Designated as Hedging Instrument \| Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt	$ 148,400,000			$ 148,400,000
Debt, weighted average interest rate, all-in	8.72%			8.72%
United Kingdom, Pounds \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt Instrument, Face Amount							42,500,000
United Kingdom, Pounds \| Interest Rate Cap \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt Instrument, Face Amount						$ 42,500,000
United Kingdom, Pounds \| 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				6.00%
United Kingdom, Pounds \| Margin over London Interbank Offered Rate (LIBOR) \| Maximum \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Derivative, Cap Interest Rate	1.25%			1.25%
Basis spread on variable rate				6.50%
United States of America, Dollars \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt Instrument, Face Amount							$ 52,400,000
United States of America, Dollars \| Interest Rate Cap \| NSM Holding Co LLC \| NSM Bank Facility
Derivative [Line Items]
Debt Instrument, Face Amount						$ 52,400,000