COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands			12 Months Ended
	Sep. 14, 2016 USD ($)	Apr. 28, 2015 USD ($)	Sep. 30, 2016 USD ($) ft²	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Purchase obligations
Purchase orders outstanding for drilling equipment			$ 44,000
LEASES
Area of leased office space (in square feet) | ft²			219,700
Fiscal Year
2017			$ 8,550
2018			5,680
2019			5,214
2020			4,401
2021			3,049
Thereafter			9,679
Total			36,573
Rent expense
Total rent expense			13,500	$ 13,600	$ 12,100
CONTINGENCIES
Gain contingencies recognized in consolidated financial statements			0
Insurance recovery receivable			50,200
Accrued liabilities
CONTINGENCIES
Settlement due			72,000
Judicial ruling | Keel accident case
CONTINGENCIES
Litigation settlement	$ 72,000
Minimum | Judicial ruling | Keel accident case
CONTINGENCIES
Damages value		$ 100,000
U.S. Land
CONTINGENCIES
Operating cost			$ 18,800