Condensed Consolidating Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 12,247	$ 46,305	$ 50,483	$ 45,644
Restricted cash	21,220	23,970
Other current assets	116,334	260,491
Total current assets	149,801	330,766
Equity investments	40,797	55,985
Unproved oil and natural gas properties and development costs not being amortized	115,377	276,025
Proved developed and undeveloped oil and natural gas properties	3,070,430	3,852,073
Accumulated depletion	(2,627,763)	(2,414,461)
Oil and natural gas properties, net	558,044	1,713,637
Other property and equipment, net	27,812	24,644
Investments in and advances to affiliates	0	0
Deferred financing costs, net	8,408	14,617
Derivative financial instruments	6,109	2,138
Goodwill	163,155	163,155
Total assets	954,126	2,304,942
Liabilities and shareholders’ equity
Current liabilities	252,919	329,436
Long-term debt	1,320,279	1,430,516
Other long-term liabilities	43,251	34,986
Payable to parent	0	0
Total shareholders' equity	(662,323)	510,004	147,905	149,393
Total liabilities and shareholders' equity	954,126	2,304,942
Resources [Member]
Current assets:
Cash and cash equivalents	34,296	86,837	81,840	65,791
Restricted cash	2,100	0
Other current assets	51,133	110,145
Total current assets	87,529	196,982
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	330,775	335,838
Accumulated depletion	(330,775)	(330,771)
Oil and natural gas properties, net	0	5,067
Other property and equipment, net	749	1,269
Investments in and advances to affiliates	616,940	1,746,931
Deferred financing costs, net	8,408	14,617
Derivative financial instruments	6,109	2,138
Goodwill	13,293	13,293
Total assets	733,028	1,980,297
Liabilities and shareholders’ equity
Current liabilities	74,472	39,506
Long-term debt	1,320,279	1,430,516
Other long-term liabilities	600	271
Payable to parent	0	0
Total shareholders' equity	(662,323)	510,004
Total liabilities and shareholders' equity	733,028	1,980,297
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(22,049)	(40,532)	(35,892)	(20,147)
Restricted cash	19,120	23,970
Other current assets	65,201	150,346
Total current assets	62,272	133,784
Equity investments	0	0
Unproved oil and natural gas properties and development costs not being amortized	115,377	276,025
Proved developed and undeveloped oil and natural gas properties	2,739,655	3,516,235
Accumulated depletion	(2,296,988)	(2,083,690)
Oil and natural gas properties, net	558,044	1,708,570
Other property and equipment, net	27,063	23,375
Investments in and advances to affiliates	0	0
Deferred financing costs, net	0	0
Derivative financial instruments	0	0
Goodwill	149,862	149,862
Total assets	797,241	2,015,591
Liabilities and shareholders’ equity
Current liabilities	178,447	289,930
Long-term debt	0	0
Other long-term liabilities	42,651	34,715
Payable to parent	2,276,594	2,058,683
Total shareholders' equity	(1,700,451)	(367,737)
Total liabilities and shareholders' equity	797,241	2,015,591
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	0	0	4,535	0
Restricted cash	0	0
Other current assets	0	0
Total current assets	0	0
Equity investments	40,797	55,985
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
Other property and equipment, net	0	0
Investments in and advances to affiliates	0	0
Deferred financing costs, net	0	0
Derivative financial instruments	0	0
Goodwill	0	0
Total assets	40,797	55,985
Liabilities and shareholders’ equity
Current liabilities	0	0
Long-term debt	0	0
Other long-term liabilities	0	0
Payable to parent	0	0
Total shareholders' equity	40,797	55,985
Total liabilities and shareholders' equity	40,797	55,985
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
Other property and equipment, net	0	0
Investments in and advances to affiliates	(616,940)	(1,746,931)
Deferred financing costs, net	0	0
Derivative financial instruments	0	0
Goodwill	0	0
Total assets	(616,940)	(1,746,931)
Liabilities and shareholders’ equity
Current liabilities	0	0
Long-term debt	0	0
Other long-term liabilities	0	0
Payable to parent	(2,276,594)	(2,058,683)
Total shareholders' equity	1,659,654	311,752
Total liabilities and shareholders' equity	$ (616,940)	$ (1,746,931)