Gabon (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 31, 2014 USD ($)	Sep. 30, 2015 USD ($) ft²	Dec. 31, 2013 km²	Sep. 30, 2015 USD ($) ft² a	Sep. 30, 2014 USD ($)
Operations [Line Items]
Impairment of oil and gas property				$ 540	$ 7,610
Oilfield inventory	$ 3,966	$ 3,426		3,426
Gabon [Member]
Operations [Line Items]
Impairment of oil and gas property	50,300
Impairment of oilfield inventory		500
Oilfield inventory		$ 3,400		$ 3,400
Dussafu PSC [Member]
Operations [Line Items]
Ownership percentage				66.667%
Area covered by acquiree entity | a				680,000
Area covered bv acquiree entity under water depths | ft²		3,000		3,000
Extended period of third exploration phase				4 years
Oil and gas properties	$ 54,300	$ 54,500		$ 54,500
3D Seismic Data [Member]
Operations [Line Items]
Processed seismic area | km²			1,260