Angolan Impairments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 31, 2015
Impaired Long Lived Assets Held And Used [Line Items]
Dry hole costs and impairments	$ 1,761,400	$ 155,800	$ 422,400	$ 1,967,180	$ 462,234	$ 236,930
Initial payment made by Sonangol	250,000		$ 250,000	250,000	$ 250,000
Block 20, offshore Angola | CIE Angola Block 20 Ltd
Impaired Long Lived Assets Held And Used [Line Items]
Percentage of working interest acquired							40.00%
Block 21, offshore Angola | CIE Angola Block 21 Ltd
Impaired Long Lived Assets Held And Used [Line Items]
Percentage of working interest acquired							40.00%
Block 20 and Block 21 | CIE Angola block 20 and block 21
Impaired Long Lived Assets Held And Used [Line Items]
Dry hole costs and impairments				1,629,800
Impairment charges				62,000
Initial payment made by Sonangol	$ 250,000			$ 250,000