PROPERTY AND EQUIPMENT (Property and Equipment by Classification) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Line Items]
Total cost	$ 4,848,014	$ 4,815,962
Less: Accumulated depreciation	(720,318)	(643,830)
Property and equipment, net	4,127,696	4,172,132	$ 3,967,028
Drilling vessels and equipment [Member]
Property, Plant and Equipment [Line Items]
Total cost	3,898,686	4,003,483
Property and equipment, net	4,000,000
Construction work in progress [Member]
Property, Plant and Equipment [Line Items]
Total cost	857,572	720,852
Drill pipe [Member]
Property, Plant and Equipment [Line Items]
Total cost	52,543	55,248
Office equipment and other [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 39,213	$ 36,379