BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Segment Performance (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Sales	$ 649,050	$ 687,974	$ 720,868	$ 740,598	$ 696,825	$ 648,872	$ 577,484	$ 564,087	$ 2,798,490	$ 2,487,268	$ 1,804,741
Operating Income (Loss)	39,021	$ (167,874)	$ 95,146	$ 54,289	24,213	$ 6,306	$ (1,164)	$ 3,609	20,582	32,964	(169,087)
Depreciation and Amortization									562,803	583,802	585,543
Total Assets	5,839,515				6,214,867				5,839,515	6,214,867
Operating Segments
Segment Reporting Information [Line Items]
Sales									2,798,490	2,487,268	1,804,741
Operating Income (Loss)									109,233	140,021	(87,545)
Depreciation and Amortization									551,465	570,662	569,997
Total Assets	5,636,209				5,656,332				5,636,209	5,656,332	5,613,084
Intersegment
Segment Reporting Information [Line Items]
Sales									0	0	0
U.S. Land
Segment Reporting Information [Line Items]
Sales									2,366,201	2,063,362	1,437,427
U.S. Land | Operating Segments
Segment Reporting Information [Line Items]
Sales									2,366,201	2,063,362	1,437,427
Operating Income (Loss)									93,088	148,251	(97,231)
Depreciation and Amortization									496,770	504,805	499,272
Total Assets	5,099,583				5,007,548				5,099,583	5,007,548	4,962,808
U.S. Land | Intersegment
Segment Reporting Information [Line Items]
Sales									0	0	0
Offshore
Segment Reporting Information [Line Items]
Sales									147,635	142,500	136,263
Offshore | Operating Segments
Segment Reporting Information [Line Items]
Sales									147,635	142,500	136,263
Operating Income (Loss)									19,594	26,124	24,201
Depreciation and Amortization									10,010	10,392	11,764
Total Assets	102,442				105,439				102,442	105,439	99,533
Offshore | Intersegment
Segment Reporting Information [Line Items]
Sales									0	0	0
International Land
Segment Reporting Information [Line Items]
Sales									211,731	238,356	212,972
International Land | Operating Segments
Segment Reporting Information [Line Items]
Sales									211,731	238,356	212,972
Operating Income (Loss)									5,366	(683)	(7,224)
Depreciation and Amortization									35,466	46,826	53,622
Total Assets	217,094				362,033				217,094	362,033	413,392
International Land | Intersegment
Segment Reporting Information [Line Items]
Sales									0	0	0
H&P Technologies
Segment Reporting Information [Line Items]
Sales									59,990	30,239	5,815
H&P Technologies | Operating Segments
Segment Reporting Information [Line Items]
Sales									59,990	30,239	5,815
Operating Income (Loss)									(12,190)	(39,554)	(13,356)
Depreciation and Amortization									7,696	7,153	3,915
Total Assets	184,558				151,787				184,558	151,787	110,468
H&P Technologies | Intersegment
Segment Reporting Information [Line Items]
Sales									0	0	0
Other
Segment Reporting Information [Line Items]
Sales									12,933	12,811	12,264
Other | Operating Segments
Segment Reporting Information [Line Items]
Sales									12,933	12,811	12,264
Operating Income (Loss)									3,375	5,883	6,065
Depreciation and Amortization									1,523	1,486	1,424
Total Assets	$ 32,532				$ 29,525				32,532	29,525	26,883
Other | Intersegment
Segment Reporting Information [Line Items]
Sales									$ 0	$ 0	$ 0