LONG-TERM DEBT (Details Textual) - USD ($)		1 Months Ended				3 Months Ended						12 Months Ended
	Feb. 10, 2014	Apr. 18, 2017	Apr. 17, 2017	Apr. 21, 2016	Apr. 17, 2015	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Dec. 31, 2017
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount						$ 738,000
Gains (Losses) on Extinguishment of Debt, Total						239,000				$ 0
Interest Expense, Total						19,281,000				20,346,000
Comcast Note [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount						11,900,000
Long-term Debt, Gross						$ 11,900,000
Debt Instrument, Interest Rate, Stated Percentage						10.47%
Debt Financing Cost [Member]
Debt Instrument [Line Items]
Interest Expense, Total						$ 715,000				$ 1,400,000
2022 Notes
Debt Instrument [Line Items]
Long-term Debt, Gross					$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage					7.375%
Debt Instrument, Description					an original issue price of 100.0% plus accrued interest
9.25% Senior Subordinated Notes due February 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross						$ 264,000,000	$ 275,000,000	$ 275,000,000				$ 275,000,000
Debt Instrument, Interest Rate, Stated Percentage						9.25%
9.25% Senior Subordinated Notes due February 2020 [Member] | Private Offering [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 335,000,000
Debt Instrument, Interest Rate, Stated Percentage	9.25%
Debt Instrument, Periodic Payment	$ 15,500,000
7.375% Senior Subordinated Notes due April 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Description					The 2022 Notes were offered at an original issue price of 100.0% plus accrued interest from April 17, 2015, and will mature on April 15, 2022. Interest on the 2022
2015 Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 350,000,000
Debt Instrument, Interest Rate Terms					At the Company’s election, the interest rate on borrowings under the 2015 Credit Facility was based on either (i) the then applicable base rate plus 3.5% (as defined in the 2015 Credit Facility) as, for any day, a rate per annum (rounded upward, if necessary, to the next 1/100th of 1%) equal to the greater of (a) the prime rate published in the Wall Street Journal, (b) a rate of 1/2 of 1% in excess rate of the overnight Federal Funds Rate at any given time, and (c) the one-month LIBOR commencing on such day plus 1.00%), or (ii) the then applicable LIBOR rate plus 4.5% (as defined in the 2015 Credit Facility). The average interest rate was approximately 5.32% for 2017 and 5.13% for 2016. Quarterly installments of 0.25%, or $875,000, of the principal balance on the term were are payable on the last day of each March, June, September and December beginning on September 30, 2015. During the three months ended March 31, 2017, the Company repaid $875,000 under the 2015 Credit Facility. The 2015 Credit Facility was terminated on April 18, 2017.
Asset Backed Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 25,000,000
Percentage Borrowing Of Eligible Accounts				85.00%
Credit Facility 2017 [Member]
Debt Instrument [Line Items]
Covenant Compliance Description For Maintaining Interest Coverage Ratio						maintaining an interest coverage ratio of no less than: § 1.25 to 1.00 on June 30, 2017 and the last day of each fiscal quarter thereafter.
Covenant Compliance Description For Maintaining Total Leverage Ratio						maintaining a senior leverage ratio of no greater than: § 5.85 to 1.00 on June 30, 2017 and the last day of each fiscal quarter thereafter.
Repayments of Long-term Debt, Total						$ 875,000
Long-term Debt, Gross						346,500,000	347,400,000	347,400,000				347,400,000
Debt Instrument, Description		The 2017 Credit Facility matures on the earlier of (i) April 18, 2023, or (ii) in the event such debt is not repaid or refinanced, 91 days prior to the maturity of either of the Company’s 2022 Notes or the Company’s 2020 Notes. At the Company’s election, the interest rate on borrowings under the 2017 Credit Facility are based on either (i) the then applicable base rate (as defined in the 2017 Credit Facility) as, for any day, a rate per annum (rounded upward, if necessary, to the next 1/100th of 1%) equal to the greater of (a) the prime rate published in the Wall Street Journal, (b) 1/2 of 1% in excess rate of the overnight Federal Funds Rate at any given time, (c) the one-month LIBOR rate commencing on such day plus 1.00%) and (d) 2%, or (ii) the then applicable LIBOR rate (as defined in the 2017 Credit Facility). The average interest rate was approximately 5.71% for 2018 and was 5.31% for 2017.
Gains (Losses) on Extinguishment of Debt, Total												7,100,000
Debt Instrument, Interest Rate Terms			The 2017 Credit Facility contains customary representations and warranties and events of default, affirmative and negative covenants (in each case, subject to materiality exceptions and qualifications) which may be more restrictive than those governing the Notes. The 2017 Credit Facility also contains certain financial covenants, including a maintenance covenant requiring the Company’s interest expense coverage ratio (defined as the ratio of consolidated EBITDA to consolidated interest expense) to be greater than or equal to 1.25 to 1.00 and its total senior secured leverage ratio (defined as the ratio of consolidated net senior secured indebtedness to consolidated EBITDA) to be less than or equal to 5.85 to 1.00.
Debt Instrument Additional Interest Payment Term On Prepayment		Beginning with the interest payment date occurring in June 2017 and ending in March 2023, the Company will be required to repay principal, to the extent then outstanding, equal to 1∕4 of 1% of the aggregate initial principal amount of all term loans incurred on the effective date of the 2017 Credit Facility.
Senior Subordinated Notes Due From 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Interest												12,700,000
Gains (Losses) on Extinguishment of Debt, Total						239,000		1,200,000			$ 690,000
Debt Instrument, Repurchase Amount						$ 11,000,000	$ 20,000,000	$ 20,000,000	$ 20,000,000			$ 20,000,000
Debt Instrument, Redemption Price, Percentage							97.375%	93.625%	96.00%