PROPERTY AND EQUIPMENT - Summary of Property and Equipment by Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Property, Plant and Equipment
Total cost	$ 4,980,205	$ 4,848,014
Less: Accumulated depreciation	(757,049)	(720,318)
Property and equipment, net	4,223,156	4,127,696
Drilling vessels and equipment
Property, Plant and Equipment
Total cost	3,909,804	3,898,686
Construction work in progress
Property, Plant and Equipment
Total cost	981,351	857,572
Drill pipe
Property, Plant and Equipment
Total cost	49,877	52,543
Office equipment and other
Property, Plant and Equipment
Total cost	$ 39,173	$ 39,213