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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Oil and gas revenues	$ 134,224	$ 83,818	$ 246,125	$ 164,533
Cost and expenses	87,606	69,012	166,044	127,347
OPERATING INCOME	46,618	14,806	80,081	37,186
Other income (expense), net	11,764	27,156	(17,726)	20,737
Income (loss) from continuing operations before income taxes	58,382	41,962	62,355	57,923
Income tax (expense) benefit	(22,545)	(16,279)	(23,994)	(21,564)
Equity in income (loss) of subsidiaries	0	0	0	0
NET INCOME FROM CONTINUING OPERATIONS	35,837	25,683	38,361	36,359
Net income from discontinued operations, net of income taxes	1,132	2,821	24,790	1,568
NET INCOME	36,969	28,504	63,151	37,927
Parent Company [Member]
Oil and gas revenues	2,086	4,608	3,647	11,397
Cost and expenses	19,315	32,806	36,433	47,352
OPERATING INCOME	(17,229)	(28,198)	(32,786)	(35,955)
Other income (expense), net	17,544	34,170	(5,681)	35,297
Income (loss) from continuing operations before income taxes	315	5,972	(38,467)	(658)
Income tax (expense) benefit	(110)	(2,041)	13,463	229
Equity in income (loss) of subsidiaries	37,519	16,320	65,459	30,473
NET INCOME FROM CONTINUING OPERATIONS	37,724	20,251	40,455	30,044
Net income from discontinued operations, net of income taxes	1,132	0	24,790	0
NET INCOME	38,856	20,251	65,245	30,044
Combined Guarantor Subsidiaries [Member]
Oil and gas revenues	132,138	79,210	242,478	153,136
Cost and expenses	68,474	51,429	129,564	94,107
OPERATING INCOME	63,664	27,781	112,914	59,029
Other income (expense), net	(5,780)	(7,014)	(12,045)	(14,560)
Income (loss) from continuing operations before income taxes	57,884	20,767	100,869	44,469
Income tax (expense) benefit	(20,365)	(7,268)	(35,410)	(15,564)
Equity in income (loss) of subsidiaries	0	0	0	0
NET INCOME FROM CONTINUING OPERATIONS	37,519	13,499	65,459	28,905
Net income from discontinued operations, net of income taxes	0	0	0	0
NET INCOME	37,519	13,499	65,459	28,905
Combined Non-Guarantor Subsidiaries [Member]
Oil and gas revenues	0	0	0	0
Cost and expenses	0	0	0	0
OPERATING INCOME	0	0	0	0
Other income (expense), net	0	0	0	0
Income (loss) from continuing operations before income taxes	0	0	0	0
Income tax (expense) benefit	0	0	0	0
Equity in income (loss) of subsidiaries	0	0	0	0
NET INCOME FROM CONTINUING OPERATIONS	0	0	0	0
Net income from discontinued operations, net of income taxes	0	2,821	0	1,568
NET INCOME	0	2,821	0	1,568
Eliminations [Member]
Oil and gas revenues	0	0	0	0
Cost and expenses	(183)	(15,223)	47	(14,112)
OPERATING INCOME	183	15,223	(47)	14,112
Other income (expense), net	0	0	0	0
Income (loss) from continuing operations before income taxes	183	15,223	(47)	14,112
Income tax (expense) benefit	(2,070)	(6,970)	(2,047)	(6,229)
Equity in income (loss) of subsidiaries	(37,519)	(16,320)	(65,459)	(30,473)
NET INCOME FROM CONTINUING OPERATIONS	(39,406)	(8,067)	(67,553)	(22,590)
Net income from discontinued operations, net of income taxes	0	0	0	0
NET INCOME	$ (39,406)	$ (8,067)	$ (67,553)	$ (22,590)