Commitments and Contingencies - Litigation (Details) - Court of Ouargla Foreign Currency Controls $ in Millions		1 Months Ended	6 Months Ended
	Dec. 31, 2006 USD ($)	Mar. 31, 2011 USD ($)	Jun. 30, 2018 USD ($)
Commitments and Contingencies, Disclosure
Litigation amount as per judgment		$ 24.1
Payment of contract amount in foreign currency	$ 7.5
Payment of contract amount in domestic currency	$ 3.2
Approximate multiplier of the amount at issue for fines and penalties			4
Maximum
Commitments and Contingencies, Disclosure
Potential judgment in excess of accrual			$ 16.1