LONG TERM DEBT AND CAPITAL LEASES - Tax-Exempt Financings (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Aggregate principal amount	$ 497,680,000	$ 525,583,000
New York Bonds, 2016
Debt Instrument [Line Items]
Principal amount		15,000,000
New York Bonds, 2014
Debt Instrument [Line Items]
Aggregate principal amount	$ 40,000,000
Debt instrument interest rate	3.75%
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 due December 2044 - fixed rate interest period through 2026; bearing interest at 3.125%
Debt Instrument [Line Items]
Debt instrument interest rate	3.125%
Aggregate principal amount	$ 15,000,000	15,000,000
Unsecured Debt \| Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-1; letter of credit backed due January 2025 - bore interest at SIFMA Index
Debt Instrument [Line Items]
Principal amount	3,600,000
Unsecured Debt \| Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-2 due January 2025 - fixed rate interest period through 2017; bore interest at 6.25%
Debt Instrument [Line Items]
Principal amount	21,400,000
Unsecured Debt \| Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 due January 2025 - fixed rate interest period through 2025; bearing interest at 5.25%
Debt Instrument [Line Items]
Principal amount	$ 25,000,000
Debt instrument interest rate	5.25%
Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 due April 2036 - fixed rate interest period through 2018; bearing interest at 4.75%
Debt Instrument [Line Items]
Debt instrument interest rate	5.125%
Aggregate principal amount	$ 15,000,000	$ 15,000,000
Additional bond issued	15,000,000
Fixed Rate Bonds \| Vermont Bonds
Debt Instrument [Line Items]
Aggregate principal amount	$ 16,000,000
Debt instrument interest rate	4.75%
New Hampshire Bonds
Debt Instrument [Line Items]
Aggregate principal amount	$ 11,000,000
Debt instrument interest rate	4.00%

Additional draw down available under the indenture.

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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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