Schedule of Prices Weighted by Field Production Related to Proved Reserves (Detail)

v2.4.0.6

Schedule of Prices Weighted by Field Production Related to Proved Reserves (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Oil
Reserve Quantities [Line Items]
Weighted price	98.13	97.36	76.28	55.87
NGLs
Reserve Quantities [Line Items]
Weighted price	47.30	51.30	44.92	33.36
Natural Gas
Reserve Quantities [Line Items]
Weighted price	2.77	4.11	4.57	3.80