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DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($)	Mar. 13, 2018	Mar. 31, 2018	Jan. 26, 2018	Sep. 30, 2017	Aug. 18, 2017	Jun. 01, 2015
Derivatives, Fair Value [Line Items]
Benchmark interest rate						3.26%
Notional amount of foreign currency derivatives						$ 125,000,000
Fair Value
Derivative assets, current		$ 26,897,000		$ 30,081,000
Derivative liabilities, current		44,792,000		46,544,000
Derivative assets, noncurrent		13,616,000		9,164,000
Derivative liabilities, noncurrent		23,603,000		11,330,000
Derivative assets		40,513,000		39,245,000
Derivative liabilities		68,395,000		57,874,000
Foreign currency contracts
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivatives		8,800,000
Treasury Lock
Derivatives, Fair Value [Line Items]
Benchmark interest rate						3.26%
Notional amount of foreign currency derivatives						$ 125,000,000
Treasury lock settlement, loss	$ 2,600,000
Natural Gas Distribution \| Not Designated as Hedging Instrument \| Physical commodity contracts
Fair Value
Derivative assets, current		88,000		151,000
Derivative liabilities, current		26,000		72,000
Natural Gas Distribution \| Not Designated as Hedging Instrument \| Financial commodity contracts
Fair Value
Derivative assets, current		375,000		0
Derivative liabilities, current		134,000		1,149,000
Natural Gas Distribution \| Not Designated as Hedging Instrument \| Interest rate contracts
Fair Value
Derivative assets, current		0		0
Derivative liabilities, current		0		8,467,000
Natural Gas Distribution \| Series Ll
Derivatives, Fair Value [Line Items]
Debt issued		$ 125,000,000
Interest rate, stated percentage		5.60%
Energy Services \| Not Designated as Hedging Instrument \| Physical commodity contracts
Fair Value
Derivative assets, current		$ 6,036,000		14,588,000
Derivative liabilities, current		16,274,000		16,589,000
Derivative assets, noncurrent		1,249,000		7,127,000
Derivative liabilities, noncurrent		14,963,000		8,710,000
Energy Services \| Not Designated as Hedging Instrument \| Financial commodity contracts
Fair Value
Derivative assets, current		20,398,000		15,302,000
Derivative liabilities, current		28,247,000		20,267,000
Derivative assets, noncurrent		12,232,000		2,033,000
Derivative liabilities, noncurrent		8,537,000		2,620,000
Energy Services \| Not Designated as Hedging Instrument \| Foreign currency contracts
Fair Value
Derivative assets, current		0		40,000
Derivative liabilities, current		97,000		0
Derivative assets, noncurrent		0		4,000
Derivative liabilities, noncurrent		103,000		0
Home Services and Other \| Not Designated as Hedging Instrument \| Physical commodity contracts
Fair Value
Derivative assets, noncurrent		135,000		0
Derivative liabilities, noncurrent		0		0
Home Services and Other \| Not Designated as Hedging Instrument \| Interest rate contracts
Fair Value
Derivative assets, current		0		0
Derivative liabilities, current		$ 14,000		$ 0
Term Loan \| Credit Agreement Due August 16, 2019
Derivatives, Fair Value [Line Items]
Debt issued					$ 100,000,000
Weighted average interest rate at end of period			2.84%