PROPERTY AND EQUIPMENT - Narrative (Details) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2017 USD ($) drillship	Dec. 13, 2016 USD ($)	Dec. 05, 2016 drillship	Feb. 28, 2017 rig	Jun. 30, 2017 USD ($) drillship	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) drillship $ / shares	Jun. 30, 2016 USD ($) $ / shares
Property, Plant and Equipment
Asset impairment					$ 211	$ (659)	$ 59,173	$ 64,773
Construction in Progress, Ultra-Deepwater Drillships | Capital Addition Purchase Commitments
Property, Plant and Equipment
Construction in progress, gross	$ 980,000				$ 980,000		$ 980,000
Number of drillships with options to delay delivery | drillship	2				2		2
Wells and Related Equipment and Facilities
Property, Plant and Equipment
Commitments on drilling units under construction	$ 324,000
Atwood Osprey
Property, Plant and Equipment
Insurance recoveries								18,000
Insurance recoveries, net of tax								$ 18,000
Insurance recoveries effect on earnings per share, after tax (in dollars per share) | $ / shares								$ 0.28
Atwood Eagle
Property, Plant and Equipment
Asset impairment							$ 59,200
Impairment, net of tax							$ 57,800
Impairment effect on earnings per share, after tax (in dollars per share) | $ / shares							$ 0.72
Atwood Eagle | Equipment
Property, Plant and Equipment
Asset impairment							$ 49,600
Atwood Eagle | Inventory
Property, Plant and Equipment
Asset impairment							8,400
Atwood Falcon
Property, Plant and Equipment
Asset impairment								$ 64,700
Impairment, net of tax								$ 64,700
Impairment effect on earnings per share, after tax (in dollars per share) | $ / shares								$ 1.00
Atwood Falcon | Equipment
Property, Plant and Equipment
Asset impairment								$ 53,000
Atwood Falcon | Inventory
Property, Plant and Equipment
Asset impairment								$ 11,700
Atwood Admiral and Atwood Archer | Ultra-Deepwater Drillships | Capital Addition Purchase Commitments
Property, Plant and Equipment
Number of drillships with options to delay delivery | drillship			2
Construction in progress, period of delivery delay			2 years
Atwood Archer | Capital Addition Purchase Commitments
Property, Plant and Equipment
Payments for construction projects		$ 125,000
Payment for construction in process, future payment, amount							15,000
Atwood Archer | Capital Addition Purchase Commitments | Final Payment
Property, Plant and Equipment
Commitments on drilling units under construction							$ 165,000
Atwood Admiral
Property, Plant and Equipment
Accelerated delivery notice period (in days)							45 days
Atwood Admiral | Capital Addition Purchase Commitments
Property, Plant and Equipment
Payment for construction in process, future payment, amount							$ 10,000
Atwood Admiral | Capital Addition Purchase Commitments | Final Payment
Property, Plant and Equipment
Commitments on drilling units under construction							$ 83,900
Hydril USA Distribution, LLC
Property, Plant and Equipment
Payments for construction projects					$ 19,000
Percent of payment upon placing the purchase order						20.00%		20.00%
Percent of payment upon completion	80.00%				80.00%		80.00%
Promissory Note | Ultra-Deepwater Drillships
Property, Plant and Equipment
Stated interest rate	5.00%				5.00%		5.00%
Australia/Southeast Asia
Property, Plant and Equipment
Number of drilling rigs | rig				3
Woodside Energy Ltd.
Property, Plant and Equipment
Contract initiation transaction costs							$ 1,000
Woodside Energy Ltd. | Atwood Osprey
Property, Plant and Equipment
Contract term, duration of contract				100 days
Woodside Energy Ltd. | Drilling Servicing Contracts | Atwood Osprey
Property, Plant and Equipment
Contract term, duration of contract				550 days