Disclosures about Oil and Natural Gas Activities (Unaudited)--Prices Used in Determining Future Net Revenues (Details)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Oil
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Price before field differentials used in determining future net revenues	96.78
Oil (including natural gas liquids)
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Price before field differentials used in determining future net revenues			94.71		96.19
Natural Gas
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Price before field differentials used in determining future net revenues	3.67		2.76		4.11
Natural Gas Liquids
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Price before field differentials used in determining future net revenues	32.53	[1]	0.00	[1]	0.00	[1]

[1] The NGL price is provided only for 2013 to coincide with our separate presentation of NGL reserves in that year.