Supplemental Oil and Natural Gas Disclosures (Unaudited) (Oil and Natural Gas Prices) (Details 3)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Oil Reserves [Member]
Oil and natural gas prices
Oil and natural gas prices	94.71	96.19	79.43
Gas Reserves [Member]
Oil and natural gas prices
Oil and natural gas prices	2.85	4.16	4.40

The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 3

-Subparagraph A

Name:	us-gaap_AverageSalesPrices
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration