COMMITMENTS, CONTINGENCIES AND LITIGATION - Narrative (Details) - USD ($)							3 Months Ended								12 Months Ended			50 Months Ended
	Aug. 28, 2018	Apr. 09, 2018	Feb. 28, 2018	Feb. 06, 2018	Apr. 06, 2017	Feb. 28, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018
Commitment Contingencies and Litigation [Line Items]
Loss on extinguishment and modification of debt															$ 0	$ 6,785,000	$ 0
Asset retirement obligation											$ 1,900,000					1,900,000
Rent expense															8,300,000	14,000,000	21,800,000
Revenues							$ 78,238,000	$ 82,972,000	$ 81,962,000	$ 74,201,000	70,035,000	$ 68,907,000	$ 69,642,000	$ 72,133,000	317,373,000	280,718,000	$ 298,297,000	$ 8,855
Revolving credit facility | Base rate
Commitment Contingencies and Litigation [Line Items]
Basis spread on variable rate							6.00%
Revolving credit facility | LIBOR
Commitment Contingencies and Litigation [Line Items]
Basis spread on variable rate							7.00%
Term Loan
Commitment Contingencies and Litigation [Line Items]
Debt balance							$ 429,143,000								429,143,000
Term loan, unamortized discount and prepaid costs							$ 13,500,000				9,800,000				$ 13,500,000	9,800,000
Term Loan | Base rate
Commitment Contingencies and Litigation [Line Items]
Basis spread on variable rate							4.75%
Term Loan | LIBOR
Commitment Contingencies and Litigation [Line Items]
Interest rate during period for the credit agreement															8.20%
Basis spread on variable rate							5.75%
Other Current Liabilities
Commitment Contingencies and Litigation [Line Items]
Asset retirement obligation							$ 2,100,000				200,000				$ 2,100,000	200,000
Other Noncurrent Liabilities
Commitment Contingencies and Litigation [Line Items]
Asset retirement obligation											1,700,000					1,700,000
Minimum
Commitment Contingencies and Litigation [Line Items]
Initial lease terms							3 years								3 years
Maximum
Commitment Contingencies and Litigation [Line Items]
Initial lease terms							25 years								25 years
Credit Agreement 2017 | Revolving credit facility
Commitment Contingencies and Litigation [Line Items]
Credit limit					$ 25,000,000.0
Debt issuance costs					400,000
Credit Agreement 2017 | Term Loan
Commitment Contingencies and Litigation [Line Items]
Credit limit					300,000,000
Debt issuance costs					5,700,000
Debt balance											$ 415,600,000					$ 415,600,000
Debt fee amount					3,300,000
Credit Agreement
Commitment Contingencies and Litigation [Line Items]
Loss on extinguishment and modification of debt					(4,800,000)
Minimum gross cash proceeds from equity offering (not less than)						$ 135,000,000
Minimum net cash proceeds from equity offering (not less than)						$ 135,000,000
Credit Agreement | LIBOR
Commitment Contingencies and Litigation [Line Items]
Basis spread on variable rate							1.00%								1.00%
Credit Agreement | Prime Rate
Commitment Contingencies and Litigation [Line Items]
Basis spread on variable rate							2.00%								2.00%
Credit Agreement | Federal Funds Effective Rate
Commitment Contingencies and Litigation [Line Items]
Basis spread on variable rate							0.50%								0.50%
Credit Agreement | Revolving credit facility
Commitment Contingencies and Litigation [Line Items]
Debt issuance costs paid														$ 1,900,000
Fifth Amendment To Credit Agreement | Revolving credit facility
Commitment Contingencies and Litigation [Line Items]
Credit limit	$ 10,000,000
Line of credit facility increase (decrease)	$ 35,000,000
Line of Credit | Credit Agreement 2017
Commitment Contingencies and Litigation [Line Items]
Debt issuance costs paid					$ 5,700,000
Line of Credit | Second Amendment To 2017 Credit Agreement
Commitment Contingencies and Litigation [Line Items]
Debt issuance costs paid				$ 1,000,000
Debt issuance costs				1,000,000
Legal fees				200,000
Debt fee amount				$ 800,000
Line of Credit | Third Amendment To 2017 Credit Agreement
Commitment Contingencies and Litigation [Line Items]
Debt issuance costs paid			$ 5,000,000
Legal fees			100,000
Debt fee amount			4,900,000
Line of Credit | Third Amendment To 2017 Credit Agreement | Term Loan
Commitment Contingencies and Litigation [Line Items]
Debt issuance costs			$ 5,000,000
Line of Credit | Fourth Amendment To Credit Agreement | Term Loan
Commitment Contingencies and Litigation [Line Items]
Debt issuance costs paid		$ 1,700,000
Interest rate increase (decrease)		(1.25%)
Debt issuance costs		$ 1,700,000
Legal fees		100,000
Debt fee amount		$ 1,600,000