Condensed Consolidating Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 45,878	$ 50,483	$ 80,442	$ 45,644
Restricted cash	15,221	20,570
Other current assets	197,494	234,801
Total current assets	258,593	305,854
Equity investments	56,514	57,562
Unproved oil and natural gas properties and development costs not being amortized	369,000	425,307
Proved developed and undeveloped oil and natural gas properties	3,736,988	3,554,210
Accumulated depletion	(2,316,974)	(2,183,464)
Oil and natural gas properties, net	1,789,014	1,796,053
Gas gathering, office, field and other equipment, net	51,388	50,339
Investments in and advances to affiliates, net	0	0
Deferred financing costs, net	35,011	28,807
Derivative financial instruments	2,773	6,829
Goodwill	163,155	163,155
Other assets	30	29
Total assets	2,356,478	2,408,628
Liabilities and shareholders’ equity
Current liabilities	398,327	349,170
Long-term debt	1,511,647	1,858,912
Deferred income taxes	0	0
Other long-term liabilities	49,922	52,641
Payable to parent	0	0
Total shareholders' equity	396,582	147,905	380,882	149,393
Total liabilities and shareholders' equity	2,356,478	2,408,628
Resources [Member]
Current assets:
Cash and cash equivalents	59,757	81,840	106,051	65,791
Restricted cash	0	0
Other current assets	11,484	22,533
Total current assets	71,241	104,373
Equity investments	0	0
Unproved oil and natural gas properties and development costs not being amortized	0	6,758
Proved developed and undeveloped oil and natural gas properties	332,418	337,972
Accumulated depletion	(330,571)	(330,086)
Oil and natural gas properties, net	1,847	14,644
Gas gathering, office, field and other equipment, net	2,410	3,479
Investments in and advances to affiliates, net	1,774,109	1,834,197
Deferred financing costs, net	34,103	27,771
Derivative financial instruments	2,756	6,829
Goodwill	13,293	13,293
Other assets	3	2
Total assets	1,899,762	2,004,588
Liabilities and shareholders’ equity
Current liabilities	71,629	76,174
Long-term debt	1,425,855	1,770,427
Deferred income taxes	0	0
Other long-term liabilities	5,696	10,082
Payable to parent	0	0
Total shareholders' equity	396,582	147,905
Total liabilities and shareholders' equity	1,899,762	2,004,588
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(21,512)	(35,892)	(29,993)	(20,147)
Restricted cash	15,221	20,570
Other current assets	180,137	206,708
Total current assets	173,846	191,386
Equity investments	0	0
Unproved oil and natural gas properties and development costs not being amortized	366,219	415,290
Proved developed and undeveloped oil and natural gas properties	3,282,905	3,097,335
Accumulated depletion	(1,965,093)	(1,840,332)
Oil and natural gas properties, net	1,684,031	1,672,293
Gas gathering, office, field and other equipment, net	27,599	24,612
Investments in and advances to affiliates, net	0	0
Deferred financing costs, net	0	0
Derivative financial instruments	0	0
Goodwill	149,862	149,862
Other assets	27	27
Total assets	2,035,365	2,038,180
Liabilities and shareholders’ equity
Current liabilities	315,170	264,485
Long-term debt	0	0
Deferred income taxes	0	0
Other long-term liabilities	35,221	33,831
Payable to parent	2,076,680	2,230,108
Total shareholders' equity	(391,706)	(490,244)
Total liabilities and shareholders' equity	2,035,365	2,038,180
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	7,633	4,535	4,384	0
Restricted cash	0	0
Other current assets	5,873	5,560
Total current assets	13,506	10,095
Equity investments	56,514	57,562
Unproved oil and natural gas properties and development costs not being amortized	2,781	3,259
Proved developed and undeveloped oil and natural gas properties	121,665	118,903
Accumulated depletion	(21,310)	(13,046)
Oil and natural gas properties, net	103,136	109,116
Gas gathering, office, field and other equipment, net	21,379	22,248
Investments in and advances to affiliates, net	0	0
Deferred financing costs, net	908	1,036
Derivative financial instruments	17	0
Goodwill	0	0
Other assets	0	0
Total assets	195,460	200,057
Liabilities and shareholders’ equity
Current liabilities	11,528	8,511
Long-term debt	85,792	88,485
Deferred income taxes	0	0
Other long-term liabilities	9,005	8,728
Payable to parent	32,466	35,777
Total shareholders' equity	56,669	58,556
Total liabilities and shareholders' equity	195,460	200,057
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Restricted cash	0	0
Other current assets	0	0
Total current assets	0	0
Equity investments	0	0
Unproved oil and natural gas properties and development costs not being amortized	0	0
Proved developed and undeveloped oil and natural gas properties	0	0
Accumulated depletion	0	0
Oil and natural gas properties, net	0	0
Gas gathering, office, field and other equipment, net	0	0
Investments in and advances to affiliates, net	(1,774,109)	(1,834,197)
Deferred financing costs, net	0	0
Derivative financial instruments	0	0
Goodwill	0	0
Other assets	0	0
Total assets	(1,774,109)	(1,834,197)
Liabilities and shareholders’ equity
Current liabilities	0	0
Long-term debt	0	0
Deferred income taxes	0	0
Other long-term liabilities	0	0
Payable to parent	(2,109,146)	(2,265,885)
Total shareholders' equity	335,037	431,688
Total liabilities and shareholders' equity	$ (1,774,109)	$ (1,834,197)