PROPERTY AND EQUIPMENT (Narrative) (Details) $ / shares in Units, $ in Thousands				1 Months Ended					3 Months Ended			12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 17, 2015 USD ($)	May 18, 2015 USD ($)	May 31, 2016 USD ($)	Aug. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Apr. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Sep. 30, 2016 USD ($) drillship $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2021 USD ($)	Sep. 30, 2016 USD ($) drillship $ / shares	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Property, Plant and Equipment [Line Items]
Asset impairment													$ 103,539	$ 60,777	$ 0
Property and equipment, net book value									$ 4,127,696				4,127,696	4,172,132	3,967,028
Net proceeds from sale of assets													20,792	(4,402)	61,516
Gain (loss) on sale of assets													(77)	$ (15,303)	$ 34,139
Construction agreement percent due upon placement of order				20.00%
Construction agreement percent due upon delivery of order				80.00%
Drilling vessels and related equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, net book value									4,000,000				4,000,000
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Asset impairment									38,600
Impairment, net of tax									$ 38,600
Impairment effect on earnings per share, after tax (in dollars per share) | $ / shares									$ 0.60
Standard Jackup Drilling Unit [Member]
Property, Plant and Equipment [Line Items]
Net proceeds from sale of assets								$ 55,400
Carrying value of equipment and related inventory								$ 20,500
Semisubmersible Tender Assist Drilling Rig [Member]
Property, Plant and Equipment [Line Items]
Net proceeds from sale of assets							$ 4,000
Carrying value of equipment and related inventory							$ 2,000
Wells and Related Equipment and Facilities [Member]
Property, Plant and Equipment [Line Items]
Construction in progress, gross									$ 845,000				845,000
Commitments on drilling units under construction													425,000
Atwood Falcon [Member]
Property, Plant and Equipment [Line Items]
Asset impairment										$ 64,900
Impairment, net of tax										$ 64,900
Impairment effect on earnings per share, after tax (in dollars per share) | $ / shares										$ 1.00
Atwood Falcon [Member] | Inventories [Member]
Property, Plant and Equipment [Line Items]
Asset impairment										$ 11,700
Atwood Falcon [Member] | Equipment [Member]
Property, Plant and Equipment [Line Items]
Asset impairment										$ 53,200
Atwood Hunter [Member]
Property, Plant and Equipment [Line Items]
Asset impairment											$ 60,800
Impairment, net of tax					$ 5,500						$ 56,100
Impairment effect on earnings per share, after tax (in dollars per share) | $ / shares					$ 0.08						$ 0.86
Net proceeds from sale of assets					$ 2,900
Gain (loss) on sale of assets					(5,500)
Cost Related to Sale of Property, Plant, and Equipment					8,700
Atwood Hunter [Member] | Inventories [Member]
Property, Plant and Equipment [Line Items]
Asset impairment											$ 8,400
Atwood Hunter [Member] | Equipment [Member]
Property, Plant and Equipment [Line Items]
Asset impairment											$ 48,000
Atwood Southern Cross [Member]
Property, Plant and Equipment [Line Items]
Impairment, net of tax						$ 7,100
Impairment effect on earnings per share, after tax (in dollars per share) | $ / shares						$ 0.11
Net proceeds from sale of assets						$ 2,100
Gain (loss) on sale of assets						$ (8,000)
Cost Related to Sale of Property, Plant, and Equipment					$ 2,000
Atwood Eagle [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense, increase (decrease)													5,800
Atwood Eagle [Member] | Scenario, Forecast [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense, increase (decrease)												$ (1,900)
Atwood Osprey [Member]
Property, Plant and Equipment [Line Items]
Insurance recoveries													18,000
Insurance recoveries, net of tax													$ 18,000
Insurance recoveries effect on earnings per share diluted, after tax (in dollars per share) | $ / shares													$ 0.28
Atwood Admiral [Member]
Property, Plant and Equipment [Line Items]
Number of drillships with options to delay delivery | drillship									2				2
Accelerated delivery notice period													45 days
Atwood Admiral [Member] | Capital Addition Purchase Commitments [Member]
Property, Plant and Equipment [Line Items]
Payments for construction in process	$ 50,000
Atwood Admiral [Member] | Final Payment [Member] | Capital Addition Purchase Commitments [Member]
Property, Plant and Equipment [Line Items]
Commitments on drilling units under construction		$ 93,900
Atwood Archer [Member] | Final Payment [Member] | Capital Addition Purchase Commitments [Member]
Property, Plant and Equipment [Line Items]
Commitments on drilling units under construction		$ 305,900
Atwood Archer [Member] | Milestone Payment No 1 [Member] | Capital Addition Purchase Commitments [Member]
Property, Plant and Equipment [Line Items]
Commitments on drilling units under construction			$ 150,000
Atwood Condor [Member] | Capital Addition Purchase Commitments [Member]
Property, Plant and Equipment [Line Items]
Construction agreement consideration				$ 19,000