BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Revenue from external customers (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Operating revenues	$ 687,974	$ 648,872	$ 2,149,440	$ 1,790,443
United States
Segment Reporting Information [Line Items]
Operating revenues	641,270	585,126	1,984,695	1,610,319
Argentina
Segment Reporting Information [Line Items]
Operating revenues	40,977	50,272	123,666	148,901
Colombia
Segment Reporting Information [Line Items]
Operating revenues	3,451	10,639	28,075	22,872
Other Foreign
Segment Reporting Information [Line Items]
Operating revenues	$ 2,276	$ 2,835	$ 13,004	$ 8,351

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration