XML 83 R114.htm IDEA: XBRL DOCUMENT v2.4.0.8
Supplemental Natural Gas and Oil Information - Additional Information (Detail)
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Annual discount rate 10.00% 10.00% 10.00%
HighMount [Member]
      
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Annual discount rate 10.00%