Acquisitions and Divestitures - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended		3 Months Ended				6 Months Ended	1 Months Ended	6 Months Ended
	Apr. 30, 2012 acre	Jun. 30, 2013	Jun. 30, 2013 Fieldwood Energy Llc [Member]	Feb. 28, 2013 Kitimat LNG [Member]	Feb. 28, 2013 Kitimat LNG [Member] Chevron Canada and Apache Canada [Member]	Feb. 28, 2013 Kitimat LNG [Member] Apache Canada [Member]	Feb. 28, 2013 Kitimat LNG [Member] Horn River and Liard Basins [Member] acre	Jun. 30, 2013 Gulf of Mexico Shelf [Member] Fieldwood Energy Llc [Member]	Jan. 31, 2012 Yara International [Member]	Jun. 30, 2013 Burrup Holdings Limited (Yara Pilbara Holdings Pty Limited ) [Member]
Business Acquisition [Line Items]
Proceeds from sale of Operations								$ 3,750,000,000
Liabilities assumed								1,500,000,000
Percentage of ownership interest in assets			50.00%
Effective date of the transaction			Jul. 01, 2013
Percentage of ownership					50.00%				49.00%
Business properties held							644,000
Percentage increase in ownership						40.00%
Proceeds from transaction		405,000,000		405,000,000
Cordillera's properties	312,000
Shares of common stock issued seller	6,272,667
Cash paid to seller	2,700,000,000
Ownership percentage by other party										51.00%
Amount paid for acquisition									$ 439,000,000