MERGER AGREEMENT WITH ENSCO PLC (Details)	Jun. 30, 2017 $ / shares	May 29, 2017 USD ($) $ / shares	Sep. 30, 2016 $ / shares
Business Acquisition [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 1.00	$ 1.00	$ 1.00
Merger with Ensco Merger Sub LLC
Business Acquisition [Line Items]
Termination fee payable upon termination		$ 30,000,000
Merger with Ensco Merger Sub LLC | Ensco PLC
Business Acquisition [Line Items]
Nominal value per share (in dollars per share) | $ / shares		$ 0.10
Maximum reimbursable expense		$ 10,000,000
Termination fee payable upon termination		$ 50,000,000
Merger with Ensco Merger Sub LLC | Ensco PLC | Common Class A
Business Acquisition [Line Items]
Stock conversion ratio		1.60