PROPERTY AND EQUIPMENT (Narrative) (Details) (USD $)	12 Months Ended
	Sep. 30, 2012 DrillingUnits	Jan. 31, 2011 option_agreement
Property, Plant and Equipment [Line Items]
Number of drilling units	5
Number of option agreements exercised		1
Expenditure on construction of drilling units in progress	$ 438,000,000
Commitments on drilling units under construction	$ 1,600,000,000
Atwood Osprey and Atwood Condor [Member]
Property, Plant and Equipment [Line Items]
Number of drilling units	2
Atwood Mako and Atwood Manta [Member]
Property, Plant and Equipment [Line Items]
Number of drilling units	2
Atwood Orca [Member]
Property, Plant and Equipment [Line Items]
Number of drilling units	1
Atwood Advantage [Member]
Property, Plant and Equipment [Line Items]
Number of drilling units	1
Atwood Achiever [Member]
Property, Plant and Equipment [Line Items]
Number of drilling units	1
Atwood Admiral [Member]
Property, Plant and Equipment [Line Items]
Number of drilling units	1