LONG-TERM DEBT - Additional information (Details 3) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2013	Dec. 31, 2016
Long-term Debt and Capital Lease Obligations, Including Current Maturities [Abstract]
Long-term Debt	$ 395,841,000		$ 281,673,000
2017	26,747,000
2018	25,697,000
2019	21,533,000
2020	15,153,000
2021	8,583,000
Thereafter	338,330,000
Loan amount attributable to interest	(373,000)
Total	395,841,000		281,673,000
Long-term debt and capital Lease Obligations, Total	435,670,000
Equipment term loans
Long-term Debt and Capital Lease Obligations, Including Current Maturities [Abstract]
2017	20,875,000
2018	20,802,000
2019	17,226,000
2020	11,516,000
2021	5,037,000
Thereafter	7,212,000
Long-term Debt	82,668,000
Total	82,668,000
Capital leases
Long-term Debt and Capital Lease Obligations, Including Current Maturities [Abstract]
2017	2,387,000
2018	1,410,000
2019	822,000
2020	152,000
2021	61,000
Thereafter	81,000
Total minimum lease payments	4,913,000
Loan amount attributable to interest	(373,000)
Total (Present value of minimum lease payments on capital leases)	4,540,000
Less current portion	(2,154,000)
Long-term capital leases	2,386,000
Senior subordinated secured debt | Main Street Capital Corporation
Loan amount		$ 20,000,000
Interest rate (as a percent)		12.00%
Paid-in-kind interest (as a percent)		2.50%
Accrued, Paid-in-kind interest added to principal balance	100,000		500,000
Accrued, Paid-in-kind, interest			100,000
Senior subordinated secured debt | Prudential Capital Partners
Loan amount		$ 20,000,000
Interest rate (as a percent)		12.00%
Paid-in-kind interest (as a percent)		2.50%
Accrued, Paid-in-kind interest added to principal balance	$ 100,000		500,000
Accrued, Paid-in-kind, interest			$ 100,000
Subordinated notes
Make-whole payment	5.00%
Subordinated notes | LST Seller notes
Loan amount	$ 22.0
Interest rate (as a percent)	10.00%
Subordinated notes | DTR Seller notes
Loan amount	$ 1.0
Interest rate (as a percent)	5.00%
Subordinated notes | BHE Seller notes
Loan amount	$ 2.0
Interest rate (as a percent)	7.00%
Term loan facility
Long-term Debt and Capital Lease Obligations, Including Current Maturities [Abstract]
2017	$ 3,485,000
2018	3,485,000
2019	3,485,000
2020	3,485,000
2021	3,485,000
Thereafter	331,037,000
Long-term Debt	348,462,000
Total	$ 348,462,000