Segment Information (Operating Income And Property And Equipment Costs Incurred) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of geographical segments	2		2
Revenue	$ 163,498	$ 153,116	$ 373,316	$ 447,318
Depletion, depreciation and accretion	13,969	14,390	42,584	47,911
Impairment of Oil and Gas Properties	135	0	135	0
Operating income (loss)	64,784	60,049	67,266	451,073
Property and equipment costs incurred	28,456	20,721	107,584	72,455
Property, plant and equipment - net	812,480		812,480		860,805
Total assets	1,268,257		1,268,257		1,369,726
UNITED STATES
Segment Reporting Information [Line Items]
Revenue	120,513	114,002	269,310	334,804
Depletion, depreciation and accretion	8,096	8,402	23,652	29,745
Impairment of Oil and Gas Properties	0		0
Operating income (loss)	57,809	56,911	78,891	456,624
Property and equipment costs incurred	20,912	15,147	85,814	50,459
Property, plant and equipment - net	415,163		415,163		451,840
Total assets	796,931		796,931		895,388
CANADA
Segment Reporting Information [Line Items]
Revenue	42,072	38,407	101,198	110,052
Depletion, depreciation and accretion	4,171	4,114	13,779	12,458
Impairment of Oil and Gas Properties	0		0
Operating income (loss)	16,364	11,076	20,199	30,126
Property and equipment costs incurred	7,254	4,288	20,924	9,972
Property, plant and equipment - net	303,827		303,827		306,423
Total assets	362,994		362,994		359,951
Midstream [Member]
Segment Reporting Information [Line Items]
Revenue	5,184	6,381	16,157	19,198
Depletion, depreciation and accretion	1,256	1,300	3,744	3,947
Impairment of Oil and Gas Properties	135		135
Operating income (loss)	2,367	3,107	7,700	9,593
Property and equipment costs incurred	72	1,615	83	2,369
Property, plant and equipment - net	89,362		89,362		97,118
Total assets	104,204		104,204		108,963
Corporate [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Depletion, depreciation and accretion	446	574	1,409	1,761
Impairment of Oil and Gas Properties	0		0
Operating income (loss)	(11,756)	(11,045)	(39,524)	(45,270)
Property and equipment costs incurred	218	(329)	763	9,655
Property, plant and equipment - net	4,128		4,128		5,424
Total assets	4,128		4,128		5,424
Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	(4,271)	(5,674)	(13,349)	(16,736)
Depletion, depreciation and accretion	0	0	0	0
Impairment of Oil and Gas Properties	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