FAIR VALUE - HIERARCHY (Details) - USD ($) $ in Thousands		6 Months Ended
		Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Assets
Other			$ 1,800
Liabilities
Impairment of available for sale securities		$ 17,800
Available-for-sale		$ 28,200
Fair Value, Measurements, Recurring
Assets
Available for sale equity securities			32,917	$ 65,752
Other	[1]		1,217	1,202
Total assets at fair value			72,090	106,199
Liabilities
Total liabilities at fair value			69,634	57,874
Fair Value, Measurements, Recurring | Physical commodity contracts
Assets
Derivative assets			11,682	21,866
Liabilities
Derivative liabilities			29,666	25,371
Fair Value, Measurements, Recurring | Financial commodity contracts
Assets
Derivative assets			25,893	17,335
Liabilities
Derivative liabilities			39,724	24,036
Fair Value, Measurements, Recurring | Foreign currency contracts
Assets
Derivative assets			0	44
Liabilities
Derivative liabilities			244
Fair Value, Measurements, Recurring | Interest rate contract
Assets
Derivative assets			381
Liabilities
Derivative liabilities				8,467
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Available for sale equity securities			32,917	65,752
Other	[1]		1,217	1,202
Total assets at fair value			53,002	84,289
Liabilities
Total liabilities at fair value			39,724	24,036
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Physical commodity contracts
Assets
Derivative assets			0	0
Liabilities
Derivative liabilities			0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Financial commodity contracts
Assets
Derivative assets			18,868	17,335
Liabilities
Derivative liabilities			39,724	24,036
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency contracts
Assets
Derivative assets			0	0
Liabilities
Derivative liabilities			0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate contract
Assets
Derivative assets			0
Liabilities
Derivative liabilities				0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets
Available for sale equity securities			0	0
Other	[1]		0	0
Total assets at fair value			19,088	21,910
Liabilities
Total liabilities at fair value			29,910	33,838
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Physical commodity contracts
Assets
Derivative assets			11,682	21,866
Liabilities
Derivative liabilities			29,666	25,371
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Financial commodity contracts
Assets
Derivative assets			7,025
Liabilities
Derivative liabilities			0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency contracts
Assets
Derivative assets			0	44
Liabilities
Derivative liabilities			244
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate contract
Assets
Derivative assets			381
Liabilities
Derivative liabilities				8,467
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets
Available for sale equity securities			0	0
Other	[1]		0	0
Total assets at fair value			0	0
Liabilities
Total liabilities at fair value			0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Physical commodity contracts
Assets
Derivative assets			0	0
Liabilities
Derivative liabilities			0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Financial commodity contracts
Assets
Derivative assets			0
Liabilities
Derivative liabilities			0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency contracts
Assets
Derivative assets			0	0
Liabilities
Derivative liabilities			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Interest rate contract
Assets
Derivative assets			$ 0
Liabilities
Derivative liabilities				$ 0

[1] Includes money market funds.