Segment Information (Operating Income And Property And Equipment Costs Incurred) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of geographical segments	2
Revenue	$ 118,703	$ 172,866
Depletion, depreciation and accretion	18,256	54,439
Impairment expense	0	317,928
Operating income (loss)	(3,874)	(267,985)
Property and equipment costs incurred	24,337	135,567
Property, plant and equipment - net	1,027,532		1,029,058
Total assets	1,309,209		1,381,788
U.S. [Member]
Segment Reporting Information [Line Items]
Revenue	81,553	141,774
Depletion, depreciation and accretion	13,128	41,823
Operating income (loss)	6,922	(107,312)
Property and equipment costs incurred	20,553	72,431
Property, plant and equipment - net	625,024		614,071
Total assets	716,093		784,104
Canada [Member]
Segment Reporting Information [Line Items]
Revenue	36,260	30,134
Depletion, depreciation and accretion	3,190	10,815
Operating income (loss)	2,841	(141,201)
Property and equipment costs incurred	3,064	53,623
Property, plant and equipment - net	289,573		294,921
Total assets	369,404		371,532
Midstream [Member]
Segment Reporting Information [Line Items]
Revenue	6,215	4,258
Depletion, depreciation and accretion	1,340	1,201
Operating income (loss)	3,124	222
Property and equipment costs incurred	80	5,980
Property, plant and equipment - net	104,968		111,523
Total assets	215,745		217,609
Corporate [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Depletion, depreciation and accretion	598	600
Operating income (loss)	(16,761)	(19,694)
Property and equipment costs incurred	640	3,533
Property, plant and equipment - net	7,967		8,543
Total assets	7,967		8,543
Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	(5,325)	(3,300)
Depletion, depreciation and accretion	0	0
Operating income (loss)	0	0
Property and equipment costs incurred	0	0
Property, plant and equipment - net	0		0
Total assets	0		0
Restricted Non-Guarantor Subsidiaries [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(778)	(147,022)
Property, plant and equipment - net	291,083		296,462
Total assets	$ 369,404		$ 371,532