Contingencies - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2012	Sep. 30, 2016	Oct. 31, 2015
Loss Contingencies [Line Items]
General and administrative		$ 16,320,000	$ 24,138,000	$ 31,071,000
Morocco [Member] | Government [Member]
Loss Contingencies [Line Items]
Recovery of contractual obligations					$ 5,500,000
Bank guarantee	$ 1,000,000
Accrued liabilities relating to our Tselfat exploration permit					5,000,000
Reversed amount in contingent liabilities previously classified as liabilities held for sale						$ 6,000,000
Bulgaria [Member]
Loss Contingencies [Line Items]
Recovery of contractual obligations					2,000,000
Estimated Litigation Liability							$ 200,000
Bulgaria [Member] | Aglen Exploration Permit Work Program [Member]
Loss Contingencies [Line Items]
General and administrative					$ 2,000,000