Supplemental Oil and Gas Information (Unaudited) Narrative (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 MMcf		Dec. 31, 2012 MMcf		Dec. 31, 2011
Reserve Quantities [Line Items]
Future net cash inflows after income taxes, annual discount rate	10.00%
Proved undeveloped reserves that had not been developed, Period	5 years
Removal of proved undeveloped reserves not developed	76		250
Changes in performance	74		291
Revision of type curve of non producing wells			88
Capital expenditures	$ 101,288		$ 485,479		$ 690,607
Barnett Shale Asset [Member] | U.S. [Member]
Reserve Quantities [Line Items]
Extensions and discoveries, Percent			96.00%		100.00%
Niobrara and West Texas Assets [Member] | U.S. [Member]
Reserve Quantities [Line Items]
Extensions and discoveries, Percent			4.00%
Horn River Asset [Member] | Canada [Member]
Reserve Quantities [Line Items]
Extensions and discoveries, Percent					97.00%
Horseshoe Canyon Asset [Member] | Canada [Member]
Reserve Quantities [Line Items]
Extensions and discoveries, Percent					3.00%
Proved Developed [Member] | U.S. [Member]
Reserve Quantities [Line Items]
Extensions and discoveries, Percent			13.00%
Proved Developed [Member] | Barnett Shale Asset [Member] | U.S. [Member]
Reserve Quantities [Line Items]
Extensions and discoveries, Percent					11.00%
Natural Gas [Member] | U.S. [Member]
Reserve Quantities [Line Items]
Revisions	234,835	[1]	(910,386)	[1]	(172,643)	[1]
Proved developed	702,147		725,361		1,244,187
Natural Gas [Member] | Canada [Member]
Reserve Quantities [Line Items]
Revisions	28,648	[1]	(33,945)	[1]	15,066	[1]
Proved developed	260,159		266,783		299,371
Oil [Member] | U.S. [Member]
Reserve Quantities [Line Items]
Revisions	62	[1]	(479)	[1]	(43)	[1]
Proved developed	139		2,416		2,545
Oil [Member] | Canada [Member]
Reserve Quantities [Line Items]
Revisions	0	[1]	0	[1]	0	[1]
Proved developed	0		0		0
Changes in Economic Factors [Member]
Reserve Quantities [Line Items]
Revisions	419,972		(590,064)		(54,539)
Changes in Non-Economic Factors [Member]
Reserve Quantities [Line Items]
Revisions	(151,615)		(629,407)		(154,405)

[1] Revisions for each period presented reflect upward (downward) changes in previous estimates attributable to changes in economic factors of 419,972 MMcfe, (590,064) MMcfe and (54,539) MMcfe in 2013, 2012 and 2011, respectively, and changes in non-economic factors of (151,615) MMcfe, (629,407) MMcfe and (154,405) MMcfe in 2013, 2012 and 2011, respectively, including:•Removal of proved undeveloped reserves that had not been developed within five years: (76) Bcfe and (250) Bcfe in 2013 and 2012, respectively;•changes in performance related to offsetting activities, higher pipeline pressures and other factors: (74) Bcfe and (291) Bcfe in 2013 and 2012, respectively and•revision of type curve of non producing wells based on comparison to producing analogs: (88) Bcfe in 2012.