Common Stock Options, Warrants And Changes In Capitalization (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended		0 Months Ended				0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Feb. 15, 2013 Utica Shale [Member] acre	Dec. 24, 2012 Utica Shale [Member] acre	Dec. 19, 2012 Utica Shale [Member] acre	Dec. 17, 2012 Utica Shale [Member] acre	Feb. 15, 2013 Common Stock [Member] Public Offering [Member]	Jan. 07, 2013 Common Stock [Member] Public Offering [Member]	Dec. 24, 2012 Common Stock [Member] Public Offering [Member]
Common Stock Options, Restricted Stock, Warrants And Changes In Capitalization [Line Items]
Issuance of common stock in public offering (shares)							8,912,500		11,750,000
Stock option, portion available to underwriters (shares)									1,650,000
Stock option, portion attributable to underwriters (shares)								900,000	750,000
Share price (usd per share)							$ 38.00		$ 38.00
Proceeds from issuance of common stock, net of offering costs	$ 359,040		$ 325,800	$ 460,700			$ 325,800		$ 460,700
Gas and oil acreage, undeveloped, net			22,000	37,000	7,000	30,000