PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) rig site	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) rig	Jun. 29, 2019 USD ($) rig
Property, Plant and Equipment [Line Items]
Net book value		$ 3,646,341	$ 4,502,084
Tangible asset impairment charges		83,500
Asset impairment charges		563,234	224,327	$ 23,128
Depreciation		474,700	556,900	578,400
Abandonments included in depreciation		4,000	11,400	27,700
Gain on sale of assets		$ 46,775	39,691	22,660
Number of industrial sites | site		6
Total consideration		$ 40,700
Real estate properties		13,500
Gain on sale of investments		27,200
Domestic And International Conventional, Flex Rig3 And Flex Rig4 Asset Groups
Property, Plant and Equipment [Line Items]
Net book value		605,800
Tangible asset impairment charges		441,400
Domestic And International Conventional, Flex Rig3 And Flex Rig4 Asset Groups | North America Solutions
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges		292,400
Domestic And International Conventional, Flex Rig3 And Flex Rig4 Asset Groups | International Solutions
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges		149,000
In Process Drilling Equipment
Property, Plant and Equipment [Line Items]
Net book value		68,400
Tangible asset impairment charges	$ 44,900
In Process Drilling Equipment | North America Solutions
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges		75,800
Rotational Inventory
Property, Plant and Equipment [Line Items]
Net book value		38,600
Tangible asset impairment charges	$ 38,600
Rotational Inventory | International Solutions
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges		$ 7,700
Domestic Flex Rig4 Asset Group
Property, Plant and Equipment [Line Items]
Net book value					$ 107,500	$ 317,800
Number of drill rigs evaluated for impairment | rig					20	71
International FlexRig4 Asset Group
Property, Plant and Equipment [Line Items]
Net book value					$ 47,800	$ 55,700
Number of drill rigs evaluated for impairment | rig					8	10
FlexRig4 Asset Group
Property, Plant and Equipment [Line Items]
Net book value						$ 235,300
Asset impairment charges			224,300
FlexRig4 Asset Group | North America Solutions
Property, Plant and Equipment [Line Items]
Asset impairment charges			216,900
FlexRig4 Asset Group | International Solutions
Property, Plant and Equipment [Line Items]
Asset impairment charges			$ 7,400
Six Conventional Rigs Asset Group
Property, Plant and Equipment [Line Items]
Net book value of certain rig components transferred				8,500
Impairment charge for assets held for sale				9,200
Impairment charge for asset held for use				1,400
Six Conventional Rigs Asset Group | International Solutions
Property, Plant and Equipment [Line Items]
Net book value				20,800
Decommissioned Rigs
Property, Plant and Equipment [Line Items]
Impairment charge for asset held for use				$ 5,700
Domestic Conventional Asset Group
Property, Plant and Equipment [Line Items]
Number of rigs decommissioned | rig		2
Flex Rig3 Asset Group
Property, Plant and Equipment [Line Items]
Number of rigs decommissioned | rig		35