Selected Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Information Disclosure [Abstract]
Oil and gas revenues	$ 107,450	$ 96,197	$ 83,818	$ 80,715	$ 55,769	$ 51,668	$ 50,672	$ 44,058	$ 368,180	$ 202,167	$ 138,123
Operating Income (Loss)	(37,151)	(24,315)	(14,808)	(22,379)	(5,164)	(16,941)	(6,281)	(9,765)	98,653	38,151	23,957
Cost and expenses									(269,527)	(164,016)	(114,166)
Net income (loss) from continuing operations	16,461	(1,860)	25,900	10,676	4,702	21,491	5,607	735	51,177	32,534	11,725
Net Income (Loss) Attributable to Parent	$ 18,490	$ (930)	$ 28,504	$ 9,423	$ 6,510	$ 21,643	$ 7,742	$ 735	$ 55,487	$ 36,629	$ 9,950
Net income from continued operations basic (in dollars per share)	$ 0.41	$ (0.05)	$ 0.65	$ 0.27	$ 0.12	$ 0.55	$ 0.14	$ 0.02	$ 1.29	$ 0.83	$ 0.34
Earnings Per Share, Basic	$ 0.47	$ (0.02)	$ 0.72	$ 0.24	$ 0.17	$ 0.56	$ 0.20	$ 0.02	$ 1.40	$ 0.94	$ 0.29
Net income from continuing operations diluted (in dollars per share)	$ 0.41	$ (0.05)	$ 0.65	$ 0.27	$ 0.12	$ 0.55	$ 0.14	$ 0.02	$ 1.28	$ 0.82	$ 0.34
Earnings Per Share, Diluted	$ 0.46	$ (0.02)	$ 0.71	$ 0.24	$ 0.16	$ 0.55	$ 0.20	$ 0.02	$ 1.39	$ 0.92	$ 0.29