Commitments and Contingencies (Details 4) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2011 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2006 USD ($)	Mar. 19, 2012 USD ($)
Court of Ouargla Customs Infringement
Commitments and Contingencies, Disclosure
Litigation amount as per judgment		$ 3,600	$ 13,600
Additional amount to be recovered		4,400
Amount paid to customs authority		3,100
Posted security paid		$ 1,330
Litigation settlement of the total fine (as a percent)		50.00%
Court of Ouargla Foreign Currency Controls
Commitments and Contingencies, Disclosure
Litigation amount as per judgment	$ 26,700
Payment of contract amount in foreign currency				$ 7,500
Payment of contract amount in domestic currency				$ 3,200
Approximate multiplier of the amount at issue for fines and penalties		4
Court of Ouargla Foreign Currency Controls | Maximum
Commitments and Contingencies, Disclosure
Potential judgment in excess of accrual		$ 18,700
NGH2L
Commitments and Contingencies, Disclosure
Escrow Deposit					$ 3,000
NGH2L | Maximum
Commitments and Contingencies, Disclosure
Monetary damages sought based on alleged breach of contract by NGH2L and alleged tortious interference with contractual relations by Parex		$ 750,000