BUSINESS SEGMENT AND GEOGRAPHIC INFORMATION - Income by Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Segment information
Total Sales	$ 720,868	$ 577,484	$ 1,461,466	$ 1,141,571
Segment Operating Income (Loss)	111,870	24,814	196,545	54,501
Depreciation	143,161	145,675	284,620	288,942
U.S. Land
Segment information
Total Sales	623,935	482,764	1,248,758	944,404
Offshore
Segment information
Total Sales	34,583	32,983	71,493	66,349
International Land
Segment information
Total Sales	50,808	52,459	117,095	115,673
H&P Technologies
Segment information
Total Sales	10,141	6,300	20,061	9,182
Other..
Segment information
Total Sales	3,447	3,265	6,921	6,470
Operating segment
Segment information
Total Sales	720,868	577,484	1,461,466	1,141,571
Segment Operating Income (Loss)	111,870	24,814	196,545	54,501
Operating segment \| U.S. Land
Segment information
Total Sales	623,935	482,729	1,248,758	944,369
Segment Operating Income (Loss)	106,139	27,075	185,807	51,820
Operating segment \| U.S. Land \| Technology
Segment information
Total Sales	1,731		2,313
Operating segment \| Offshore
Segment information
Total Sales	34,583	32,983	71,493	66,349
Segment Operating Income (Loss)	4,531	5,449	11,699	14,174
Operating segment \| International Land
Segment information
Total Sales	50,808	52,459	117,095	115,673
Segment Operating Income (Loss)	7,968	(695)	14,597	2,839
Operating segment \| H&P Technologies
Segment information
Total Sales	8,327	6,300	17,665	9,149
Segment Operating Income (Loss)	(7,933)	(8,533)	(18,277)	(17,348)
Operating segment \| Other..
Segment information
Total Sales	3,215	3,013	6,455	6,031
Segment Operating Income (Loss)	1,165	1,518	2,719	3,016
Inter-Segment
Segment information
Total Sales	(2,046)	(287)	(2,862)	(507)
Inter-Segment \| U.S. Land
Segment information
Total Sales		35		35
Inter-Segment \| H&P Technologies
Segment information
Total Sales	1,814		2,396	33
Inter-Segment \| Other..
Segment information
Total Sales	$ 232	$ 252	$ 466	$ 439

Amount of operating income (loss) attributed to the reportable segment.

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- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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