Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					3 Months Ended
	Mar. 31, 2013 Contract acre	Aug. 01, 2012 acre	May 15, 2008	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Lease agreements [Member]	Mar. 31, 2013 Lease agreements [Member] Area of Land [Member] sqft	Dec. 31, 2012 Lease agreements [Member] Area of Land [Member] Maximum [Member] sqft	Dec. 31, 2012 Lease agreements [Member] Area of Land [Member] Minimum [Member] sqft
Commitments and Contingencies (Textual) [Abstract]
Office space of headquarters								36,525	28,743
Increased office space of headquarters							7,782
Potential loss to the company				$ 7	$ 0
Transportation and processing fee under the agreement						0.3
Commitments and Contingencies (Additional Textual) [Abstract]
Lease period	Jun. 30, 2022
Minimum delivery commitment to avoid paying gas deficiency fee	80.00%
Percentage of minimum delivery commitment to anticipated production	80.00%
Undiscounted minimum commitments	15.2
Maximum termination outstanding obligations of contracts	4.6
Minimum outstanding commitments	4.3
Issue on the deep rights below the Cotton Valley formation	1,805
Right to participate in working capital	25.00%
Company's total revenue and overriding royalty interests on the acreage range Minimum	2.00%
Company's total revenue and overriding royalty interests on the acreage range Maximum	23.00%
Loss contingency, lawsuit filing date	May 15, 2008
Royalty owner undivided interest in mineral			0.167
Acres reformed by court		169
Rights on remaining acres		1,636
Consent to the proposed assignment	50.00%
Remittance submitted to company	8.7
Amount received by the company as remittance fee	$ 4.3
The amount recovered from company	300.00%
Lease expiring period	Jun. 30, 2022
Extension of contracts	6 months
Natural gas processing and transportation agreement	5 years
Number of drilling rig contracts	2
Term of new drilling rig contracts	9 months