Segment Information (Operating Income And Property And Equipment Costs Incurred) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of geographical segments	2		2
Revenue	$ 118,032	$ 175,497	$ 209,818	$ 294,201
Depletion, depreciation and accretion	14,659	15,265	28,615	33,521
Operating income (loss)	13,536	394,894	2,482	391,022
Property and equipment costs incurred	36,857	27,399	79,128	51,736
Property, plant and equipment - net	815,331		815,331		860,805
Total assets	1,059,047		1,059,047		1,369,726
UNITED STATES
Segment Reporting Information [Line Items]
Revenue	85,894	140,393	148,797	221,949
Depletion, depreciation and accretion	8,176	10,323	15,556	23,451
Operating income (loss)	18,901	392,786	21,081	399,710
Property and equipment costs incurred	31,686	14,760	64,902	35,313
Property, plant and equipment - net	402,791		402,791		451,840
Total assets	588,817		588,817		895,388
CANADA
Segment Reporting Information [Line Items]
Revenue	31,164	34,264	59,126	70,523
Depletion, depreciation and accretion	4,781	3,047	9,608	6,237
Operating income (loss)	4,445	16,209	3,835	19,050
Property and equipment costs incurred	4,717	2,620	13,670	5,684
Property, plant and equipment - net	313,669		313,669		306,423
Total assets	357,494		357,494		359,951
Midstream [Member]
Segment Reporting Information [Line Items]
Revenue	5,110	6,576	10,973	12,791
Depletion, depreciation and accretion	1,245	1,307	2,488	2,647
Operating income (loss)	2,132	3,362	5,334	6,486
Property and equipment costs incurred	0	675	11	755
Property, plant and equipment - net	94,306		94,306		97,118
Total assets	108,171		108,171		108,963
Corporate [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Depletion, depreciation and accretion	457	588	963	1,186
Operating income (loss)	(11,942)	(17,463)	(27,768)	(34,224)
Property and equipment costs incurred	454	9,344	545	9,984
Property, plant and equipment - net	4,565		4,565		5,424
Total assets	4,565		4,565		5,424
Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	(4,136)	(5,736)	(9,078)	(11,062)
Depletion, depreciation and accretion	0	0	0	0
Operating income (loss)	0	0	0	0
Property and equipment costs incurred	0	0	0	0
Property, plant and equipment - net	0		0		0
Total assets	$ 0		$ 0		$ 0