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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands | Jun. 30, 2019 | Sep. 30, 2018 | Jun. 30, 2018 | Sep. 30, 2017
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RESTRICTED Cash and Investments [Abstract] |  |  |  |
Cash | $ 334,775 | $ 284,355 | $ 306,426 | $ 521,375
Restricted cash | 34,300 | 41,800 | 41,500 | 39,100
Total cash, cash equivalents, and restricted cash | 369,106 | 326,185 | 347,942 | 560,509
Restricted cash from initial capitalization of captive insurance company | 2,000 | 2,000 |  |
Additional cash restricted at the election of management for potential insurance claims | 29,300 | 28,500 |  |
Drilling technology companies |  |  |  |
RESTRICTED Cash and Investments [Abstract] |  |  |  |
Restricted cash | 3,000 | 11,300 |  |
Prepaid expenses and other |  |  |  |
RESTRICTED Cash and Investments [Abstract] |  |  |  |
Restricted cash | 30,543 | 39,830 | 34,614 | 32,439
Other assets |  |  |  |
RESTRICTED Cash and Investments [Abstract] |  |  |  |
Restricted cash | 3,788 | $ 2,000 | $ 6,902 | $ 6,695
United States |  |  |  |
RESTRICTED Cash and Investments [Abstract] |  |  |  |
Cash | 318,900 |  |  |
Other countries |  |  |  |
RESTRICTED Cash and Investments [Abstract] |  |  |  |
Cash | $ 15,900 |  |  |

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- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3044-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(2)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=98513485&loc=SL98516268-108586 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(1)(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3044-108585 + Details
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