SEGMENT INFORMATION - Revenue from external customers and long lived assets (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Segment information
Operating revenues	$ 331,708	$ 366,486	$ 438,191	$ 487,847	$ 553,800	$ 661,445	$ 885,670	$ 1,060,787	$ 1,624,232	$ 3,161,702	$ 3,715,968
Long-Lived Assets	5,144,733				5,563,170				5,144,733	5,563,170	$ 5,187,587
Accounts receivable, net of reserve	375,169				445,948				$ 375,169	$ 445,948
Operating revenues | Customer concentration | Customer one
Segment information
Concentration percentage									11.90%	10.10%	10.70%
Operating revenues | Customer concentration | Customer two
Segment information
Concentration percentage									9.40%	4.60%	2.90%
Receivables | Customer concentration
Segment information
Accounts receivable, net of reserve	49,500				101,300				$ 49,500	$ 101,300
United States
Segment information
Operating revenues									1,386,786	2,750,043	$ 3,338,365
Long-Lived Assets	4,804,328				5,149,315				4,804,328	5,149,315	4,753,844
Argentina
Segment information
Operating revenues									159,427	177,984	107,189
Long-Lived Assets	183,286				211,862				183,286	211,862	145,783
Colombia
Segment information
Operating revenues									20,488	70,076	81,168
Long-Lived Assets	91,815				102,401				91,815	102,401	105,842
Ecuador
Segment information
Operating revenues									4,948	30,987	67,976
Long-Lived Assets	438				28,918				438	28,918	71,011
Other foreign
Segment information
Operating revenues									52,583	132,612	121,270
Long-Lived Assets	$ 64,866				$ 70,674				$ 64,866	$ 70,674	$ 111,107