Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statement Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Oil and gas revenues	$ 83,818	$ 50,672	$ 164,533	$ 94,730
Cost and expenses	69,099	44,634	127,513	78,927
Operating income (loss)	14,719	6,038	37,020	15,803
Other income and (expense), net	28,595	5,306	19,735	(2,664)
Income (loss) before income taxes	43,314	11,344	56,755	13,139
Income tax (expense) benefit	(14,810)	(3,602)	(18,828)	(4,662)
Equity in income (loss) of subsidiaries	0	0	0	0
Net income (loss)	28,504	7,742	37,927	8,477
Parent Company [Member]
Oil and gas revenues	4,608	9,389	11,397	18,164
Cost and expenses	32,818	21,788	47,365	37,969
Operating income (loss)	(28,210)	(12,399)	(35,968)	(19,805)
Other income and (expense), net	34,187	15,242	35,314	11,098
Income (loss) before income taxes	5,977	2,843	(654)	(8,707)
Income tax (expense) benefit	(2,092)	(784)	229	3,059
Equity in income (loss) of subsidiaries	16,166	4,713	30,269	12,334
Net income (loss)	20,051	6,772	29,844	6,686
Combined Guarantor Subsidiaries [Member]
Oil and gas revenues	79,210	41,283	153,136	76,566
Cost and expenses	51,429	24,237	94,107	43,647
Operating income (loss)	27,781	17,046	59,029	32,919
Other income and (expense), net	(7,014)	(8,255)	(14,560)	(12,081)
Income (loss) before income taxes	20,767	8,791	44,469	20,838
Income tax (expense) benefit	(7,268)	(3,230)	(15,564)	(7,656)
Equity in income (loss) of subsidiaries	0	0	0	0
Net income (loss)	13,499	5,561	28,905	13,182
Combined Non-Guarantor Subsidiaries [Member]
Oil and gas revenues	0	0	0	0
Cost and expenses	75	143	153	143
Operating income (loss)	(75)	(143)	(153)	(143)
Other income and (expense), net	1,422	(1,681)	(1,019)	(1,681)
Income (loss) before income taxes	1,347	(1,824)	(1,172)	(1,824)
Income tax (expense) benefit	1,320	976	2,536	976
Equity in income (loss) of subsidiaries	0	0	0	0
Net income (loss)	2,667	(848)	1,364	(848)
Eliminations [Member]
Oil and gas revenues	0	0	0	0
Cost and expenses	(15,223)	(1,534)	(14,112)	(2,832)
Operating income (loss)	15,223	1,534	14,112	2,832
Other income and (expense), net	0	0	0	0
Income (loss) before income taxes	15,223	1,534	14,112	2,832
Income tax (expense) benefit	(6,770)	(564)	(6,029)	(1,041)
Equity in income (loss) of subsidiaries	(16,166)	(4,713)	(30,269)	(12,334)
Net income (loss)	$ (7,713)	$ (3,743)	$ (22,186)	$ (10,543)