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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Oil and gas revenues	$ 129,728	$ 144,329	$ 134,224	$ 111,901	$ 107,450	$ 96,197	$ 83,818	$ 80,715	$ 520,182	$ 368,180	$ 202,167
Operating income (loss)	(21,002)	48,603	46,618	33,463	37,151	24,318	14,806	22,380	107,682	98,653	38,151
Net income from continuing operations	(22,215)	5,712	35,837	2,524	16,763	(1,945)	25,683	10,676	21,858	51,177	32,534
Net income (loss)	$ (23,989)	$ 4,521	$ 36,969	$ 26,182	$ 18,490	$ (930)	$ 28,504	$ 9,423	$ 43,683	$ 55,487	$ 36,629
Net income from continued operations basic (in dollars per share)	$ (0.52)	$ 0.14	$ 0.89	$ 0.06	$ 0.42	$ (0.05)	$ 0.65	$ 0.27	$ 0.54	$ 1.29	$ 0.83
Net income per share basic (in dollars per share)	$ (0.56)	$ 0.11	$ 0.92	$ 0.66	$ 0.47	$ (0.02)	$ 0.72	$ 0.24	$ 1.07	$ 1.40	$ 0.94
Net income from continuing operations diluted (in dollars per share)	$ (0.52)	$ 0.14	$ 0.88	$ 0.06	$ 0.42	$ (0.05)	$ 0.64	$ 0.27	$ 0.53	$ 1.28	$ 0.82
Net income per share, diluted (in dollars per share)	$ (0.56)	$ 0.11	$ 0.91	$ 0.65	$ 0.46	$ (0.02)	$ 0.71	$ 0.24	$ 1.06	$ 1.39	$ 0.92