ACQUISITIONS Total Identifiable Net Assets Acquired (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012 Merit Acquisition [Member]	Dec. 31, 2011 Seneca Upshur [Domain]	Dec. 31, 2011 2003/2002-D Partnerships [Member]	Dec. 31, 2011 2005 Partnerships [Member]
Business Acquisition [Line Items]
Total acquisition cost	$ 304,643	$ 69,618	$ 29,960	$ 43,015
Natural gas and crude oil properties - proved	180,696	20,175	27,940	39,825
Natural gas and crude oil properties - unproved	151,428	49,100	0	0
Other assets	3,631	10,196	3,455	3,848
Total assets acquired	335,755	79,471	31,395	43,673
Asset retirement obligation	14,833	8,157	497	300
Other accrued expenses	9,574	0	0	0
Other Liabilities	6,705	1,696	938	358
Total liabilities assumed	$ 31,112	$ 9,853	$ 1,435	$ 658