PROPERTY AND EQUIPMENT (Property and Equipment by Classification) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Property, Plant and Equipment [Line Items]
Cost	$ 3,746,005	$ 3,002,162
Less: Accumulated depreciation	(581,281)	(464,822)
Drilling and other property and equipment, net	3,164,724	2,537,340	1,887,321
Drilling vessels equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	2,979,503	2,523,895
Construction work in progress [Member]
Property, Plant and Equipment [Line Items]
Cost	715,320	438,081
Drill pipe [Member]
Property, Plant and Equipment [Line Items]
Cost	26,743	20,576
Office equipment and other [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 24,439	$ 19,610