LONG-TERM DEBT - Tax-Exempt Offerings (Details) - Unsecured Debt - USD ($)	3 Months Ended
Jun. 30, 2018	Mar. 31, 2017
Finance Authority Of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2
Debt Instrument [Line Items]
Aggregate principal amount	$ 15,000,000
Debt instrument interest rate percentage	4.375%
VEDA Bonds
Debt Instrument [Line Items]
Aggregate principal amount	$ 16,000,000
Debt instrument interest rate percentage	4.75%
Debt instrument, interest rate during period	4.625%
Revenue Bonds Series Two Thousand Five Rone Due Two Thousand Twenty Five
Debt Instrument [Line Items]
Aggregate principal amount		$ 3,600,000
Revenue Bonds Series Two Thousand Five Rtwo Due Two Thousand Twenty Five
Debt Instrument [Line Items]
Aggregate principal amount		21,400,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 (FAME Bonds 2005R-3)
Debt Instrument [Line Items]
Aggregate principal amount		$ 25,000,000
Debt instrument interest rate percentage		5.25%

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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The average effective interest rate during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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