PROPERTY, PLANT AND EQUIPMENT - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 7,353,541	$ 8,486,200
Accumulated depreciation	(4,226,254)	(4,839,859)
Property, plant and equipment, net	3,127,287	3,646,341
Assets held-for-sale	71,453	0
Drilling services equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 6,229,011	7,313,234
Drilling services equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Drilling services equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	15 years
Tubulars
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Property, plant and equipment, gross	$ 573,900	615,281
Real estate properties
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 43,302	43,389
Real estate properties \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Real estate properties \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	45 years
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 459,741	464,704
Other \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	2 years
Other \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	23 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 47,587	$ 49,592

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of assets held-for-sale that are not part of a disposal group, expected to be sold within a year or the normal operating cycle, if longer.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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