PROPERTY, PLANT AND EQUIPMENT - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
PROPERTY, PLANT AND EQUIPMENT
Gross, property, plant and equipment	$ 9,146,247	$ 8,882,934
Accumulated depreciation	(4,288,865)	(3,881,883)
Property, plant and equipment, net	4,857,382	5,001,051	$ 5,144,733
Contract drilling equipment
PROPERTY, PLANT AND EQUIPMENT
Gross, property, plant and equipment	$ 8,442,081	8,197,572
Contract drilling equipment | Minimum
PROPERTY, PLANT AND EQUIPMENT
Estimated Useful Lives	4 years
Contract drilling equipment | Maximum
PROPERTY, PLANT AND EQUIPMENT
Estimated Useful Lives	15 years
Real estate properties
PROPERTY, PLANT AND EQUIPMENT
Gross, property, plant and equipment	$ 68,888	66,005
Real estate properties | Minimum
PROPERTY, PLANT AND EQUIPMENT
Estimated Useful Lives	10 years
Real estate properties | Maximum
PROPERTY, PLANT AND EQUIPMENT
Estimated Useful Lives	45 years
Other.
PROPERTY, PLANT AND EQUIPMENT
Gross, property, plant and equipment	$ 471,310	450,031
Other. | Minimum
PROPERTY, PLANT AND EQUIPMENT
Estimated Useful Lives	2 years
Other. | Maximum
PROPERTY, PLANT AND EQUIPMENT
Estimated Useful Lives	23 years
Construction in progress
PROPERTY, PLANT AND EQUIPMENT
Gross, property, plant and equipment	$ 163,968	$ 169,326