Supplemental Oil and Gas Disclosures (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Capitalized costs relating to oil and gas producing activities [Abstract]
Proved oil and gas properties	$ 564,755	$ 563,317
Unproved properties	0	2,089
Total	564,755	565,406
Accumulated depreciation, depletion, amortization and impairment	(413,704)	(383,469)
Net capitalized costs	151,051	181,937
Cost incurred in oil and gas property acquisition and development activities [Abstract]
Development costs	93,878	56,318	46,735
Exploration costs	0	0	8,410
Property acquisition costs	0	7,200	0
Unproved	0	989	1,100
Total	93,878	64,507	56,245
Results of operations for oil and gas producing activities [Abstract]
Revenues	94,275	68,499	64,615
Production costs	(33,871)	(31,419)	(27,347)
Depreciation, depletion, and amortization	(26,072)	(22,767)	(15,595)
Proved property impairment	(6,025)	(19,774)	0
General and administrative	(3,350)	(2,679)	(2,352)
Results of operations from oil and gas producing activities (excluding corporate overhead and interest costs)	24,957	(8,140)	19,321
Depletion per barrel of oil equivalent	16.59	15.59	12.26
Oil/NGL [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	19,956,000	14,219,000	9,794,000
Revisions of previous estimates	999,000	1,574,000	2,290,000
Extensions and discoveries	10,746,000	5,809,000	2,703,000
Purchases of minerals in place	0	1,000
Sales of minerals in place	(7,748,000)	(850,000)	0
Production	1,000,000	797,000	568,000
Balance	22,953,000	19,956,000	14,219,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	8,310,000	8,650,000	7,761,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	14,640,000	11,306,000	6,460,000
Natural Gas [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	61,184,000	72,075,000	84,913,000
Revisions of previous estimates	(5,123,000)	(7,470,000)	(13,009,000)
Extensions and discoveries	3,610,000	6,983,000	4,393,000
Purchases of minerals in place	0	69,000
Sales of minerals in place	(8,141,000)	(6,376,000)	0
Production	3,421,000	4,097,000	4,222,000
Balance	48,109,000	61,184,000	72,075,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	31,572,000	41,220,000	42,582,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	16,537,000	19,964,000	29,493,000
Oil Equivalents [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	30,152,000	26,232,000	23,947,000
Revisions of previous estimates	145,000	328,000	122,000
Extensions and discoveries	11,348,000	6,973,000	3,435,000
Purchases of minerals in place	0	13,000
Sales of minerals in place	(9,105,000)	(1,913,000)	0
Production	1,570,000	1,481,000	1,272,000
Balance	30,970,000	30,152,000	26,232,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	13,572,000	15,520,000	14,858,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	17,397,000	14,634,000	11,376,000
U.S. [Member]
Capitalized costs relating to oil and gas producing activities [Abstract]
Proved oil and gas properties	530,996	531,971
Unproved properties	0	0
Total	530,996	531,971
Accumulated depreciation, depletion, amortization and impairment	(381,283)	(356,255)
Net capitalized costs	149,713	175,716
Cost incurred in oil and gas property acquisition and development activities [Abstract]
Development costs	91,325	48,283	32,471
Exploration costs	0	0	8,410
Property acquisition costs	0	7,200	0
Unproved	0	0	0
Total	91,325	55,483	40,881
Results of operations for oil and gas producing activities [Abstract]
Revenues	92,268	65,590	63,105
Production costs	(31,642)	(29,166)	(26,552)
Depreciation, depletion, and amortization	(25,028)	(20,704)	(14,914)
Proved property impairment	0	0	0
General and administrative	(2,471)	(1,980)	(1,698)
Results of operations from oil and gas producing activities (excluding corporate overhead and interest costs)	33,127	13,740	19,941
Depletion per barrel of oil equivalent	16.32	14.74	11.96
U.S. [Member] | Oil/NGL [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	19,751,000	13,780,000	9,718,000
Revisions of previous estimates	1,073,000	1,774,000	2,290,000
Extensions and discoveries	10,746,000	5,809,000	2,326,000
Purchases of minerals in place	0	1,000
Sales of minerals in place	(7,748,000)	(850,000)	0
Production	976,000	763,000	554,000
Balance	22,846,000	19,751,000	13,780,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	8,284,000	8,531,000	7,433,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	14,560,000	11,220,000	6,348,000
U.S. [Member] | Natural Gas [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	60,099,000	69,191,000	84,523,000
Revisions of previous estimates	(4,804,000)	(5,786,000)	(13,009,000)
Extensions and discoveries	3,610,000	6,983,000	1,837,000
Purchases of minerals in place	0	69,000
Sales of minerals in place	(8,141,000)	(6,376,000)	0
Production	3,343,000	3,982,000	4,160,000
Balance	47,421,000	60,099,000	69,191,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	31,424,000	40,723,000	40,451,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	15,996,000	19,376,000	28,740,000
U.S. [Member] | Oil Equivalents [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	29,768,000	25,313,000	23,806,000
Revisions of previous estimates	270,000	809,000	122,000
Extensions and discoveries	11,348,000	6,973,000	2,632,000
Purchases of minerals in place	0	13,000
Sales of minerals in place	(9,105,000)	(1,913,000)	0
Production	1,533,000	1,427,000	1,247,000
Balance	30,748,000	29,768,000	25,313,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	13,521,000	15,318,000	14,175,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	17,226,000	14,450,000	11,138,000
Canada [Member]
Capitalized costs relating to oil and gas producing activities [Abstract]
Proved oil and gas properties	33,759	31,346
Unproved properties	0	2,089
Total	33,759	33,435
Accumulated depreciation, depletion, amortization and impairment	(32,421)	(27,214)
Net capitalized costs	1,338	6,221
Cost incurred in oil and gas property acquisition and development activities [Abstract]
Development costs	2,553	8,035	14,264
Exploration costs	0	0	0
Property acquisition costs	0	0	0
Unproved	0	989	1,100
Total	2,553	9,024	15,364
Results of operations for oil and gas producing activities [Abstract]
Revenues	2,007	2,909	1,510
Production costs	(2,229)	(2,253)	(795)
Depreciation, depletion, and amortization	(1,044)	(2,063)	(681)
Proved property impairment	(6,025)	(19,774)	0
General and administrative	(879)	(699)	(654)
Results of operations from oil and gas producing activities (excluding corporate overhead and interest costs)	$ (8,170)	$ (21,880)	$ (620)
Depletion per barrel of oil equivalent	27.37	37.48	27.58
Canada [Member] | Oil/NGL [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	205,000	439,000	76,000
Revisions of previous estimates	(74,000)	(200,000)	0
Extensions and discoveries	0	0	377,000
Purchases of minerals in place	0	0
Sales of minerals in place	0	0	0
Production	24,000	34,000	14,000
Balance	107,000	205,000	439,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	26,000	119,000	328,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	80,000	86,000	112,000
Canada [Member] | Natural Gas [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	1,085,000	2,884,000	390,000
Revisions of previous estimates	(319,000)	(1,684,000)	0
Extensions and discoveries	0	0	2,556,000
Purchases of minerals in place	0	0
Sales of minerals in place	0	0	0
Production	78,000	115,000	62,000
Balance	688,000	1,085,000	2,884,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	148,000	497,000	2,131,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	541,000	588,000	753,000
Canada [Member] | Oil Equivalents [Member]
Proved developed and undeveloped reserves [Abstract]
Balance	384,000	919,000	141,000
Revisions of previous estimates	(125,000)	(481,000)	0
Extensions and discoveries	0	0	803,000
Purchases of minerals in place	0	0
Sales of minerals in place	0	0	0
Production	37,000	54,000	25,000
Balance	222,000	384,000	919,000
Proved Developed Reserves [Abstract]
Proved Developed Reserves	51,000	202,000	683,000
Proved Undeveloped Reserves [Abstract]
Proved Undeveloped Reserves	171,000	184,000	238,000