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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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BUSINESS SEGMENT AND GEOGRAPHIC INFORMATION - Income by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment information
Total Sales	$ 696,825	$ 648,872	$ 577,484	$ 564,087	$ 532,304	$ 498,564	$ 405,283	$ 368,590	$ 2,487,268	$ 1,804,741	$ 1,624,232
Segment Operating Income (Loss)									148,349	(87,352)	68,200
Depreciation									583,802	585,543	598,587
Total Assets	6,214,867				6,439,985				6,214,867	6,439,985	6,831,955
Additions to Long-Lived Assets									468,830	408,106	241,290
U.S. Land
Segment information
Total Sales									2,069,384	1,439,523	1,242,462
Segment Operating Income (Loss)									150,698	(94,880)	74,118
Depreciation									505,112	499,486	508,237
Total Assets	5,012,378				4,967,074				5,012,378	4,967,074	5,005,299
Additions to Long-Lived Assets									441,624	394,508	209,156
Offshore
Segment information
Total Sales									142,500	136,263	138,601
Segment Operating Income (Loss)									26,124	24,201	15,659
Depreciation									10,392	11,764	12,495
Total Assets	105,439				99,533				105,439	99,533	105,152
Additions to Long-Lived Assets									4,326	2,847	9,694
International Land
Segment information
Total Sales									238,356	212,972	229,894
Segment Operating Income (Loss)									(683)	(7,224)	(14,086)
Depreciation									46,826	53,622	57,102
Total Assets	362,033				413,392				362,033	413,392	487,181
Additions to Long-Lived Assets									4,424	3,400	2,364
Other
Segment information
Total Sales									39,243	16,845	14,130
Segment Operating Income (Loss)									(27,790)	(9,449)	(7,491)
Depreciation									21,472	20,671	20,753
Total Assets	$ 735,017				$ 959,986				735,017	959,986	1,234,323
Additions to Long-Lived Assets									18,456	7,351	20,076
Operating segment
Segment information
Total Sales									2,487,268	1,804,741	1,624,232
Operating segment \| U.S. Land
Segment information
Total Sales									2,068,195	1,439,523	1,242,462
Operating segment \| Offshore
Segment information
Total Sales									142,500	136,263	138,601
Operating segment \| International Land
Segment information
Total Sales									238,356	212,972	229,894
Operating segment \| Other
Segment information
Total Sales									38,217	15,983	13,275
Inter-Segment
Segment information
Total Sales									(2,215)	(862)	(855)
Inter-Segment \| U.S. Land
Segment information
Total Sales									1,189
Inter-Segment \| Other
Segment information
Total Sales									$ 1,026	$ 862	$ 855