Supplemental Gas Data Acreages (Details)	12 Months Ended
	Dec. 31, 2011 A
Gas and Oil Acreage [Line Items]
Productive Gas Wells, Number of Wells, Gross	14,743,000
Productive Gas Wells, Number of Wells, Net	12,725,000
Gas and Oil Acreage, Developed, Gross	507,949,000
Gas and Oil Acreage, Developed, Net	421,874,000
Gas and Oil Acreage, Undeveloped, Gross	146,479,000
Gas and Oil Acreage, Undeveloped, Net	124,276,000
unproved acreage gross	5,035,749,000
Gas and Oil Acreage, Unproved, Net	4,040,598,000