Commitments And Contingencies (Details) a in Millions, CAD in Millions, ft³ in Billions		1 Months Ended				12 Months Ended
	Nov. 17, 2015 item	Sep. 30, 2015 plaintiff item	Jul. 31, 2013 USD ($)	Aug. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2015 USD ($) ft³	Dec. 31, 2015 CAD item	Dec. 31, 2015 USD ($) item	Mar. 31, 2010 CAD a
Commitments And Contingencies [Line Items]
Future demand transportation charges, 2016								$ 623,000,000
Future demand transportation charges, 2017								691,000,000
Future demand transportation charges, 2018								712,000,000
Future demand transportation charges, 2019								751,000,000
Future demand transportation charges, 2020								702,000,000
Future demand transportation charges, thereafter								5,402,000,000
Total future demand transportation charges due								8,900,000,000
Guarantee obligations relative to the firms transportation agreements and gathering project and services								960,000,000
Option to reduce obligation under transportation agreement						$ 100,000,000
Option to reduce volume obligation under transportation agreement | ft³						531
Lease expiration date						Dec. 31, 2027
Operating leases, future minimum payments, 2016								71,000,000
Operating leases, future minimum payments, 2017								64,000,000
Operating leases, future minimum payments, 2018								44,000,000
Operating leases, future minimum payments, 2019								38,000,000
Operating leases, future minimum payments, 2020								30,000,000
Operating leases, future minimum payments, thereafter								28,000,000
Litigation settlement, gross					$ 11,000,000
Litigation, portion of profits considered for disgorgement					$ 382,000,000
Actual damages recoverable by plaintiff per August 2011 judgement				$ 11,000,000
Disgorgement recoverable by plaintiff per August 2011 judgement				24,000,000
Prejudgement interest and attorney's fees recoverable by plaintiff per August 2011 judgement				$ 9,000,000
Disgorgement recoverable by plaintiff to be reversed			$ 24,000,000
Actual damages recoverable by plaintiff to be reversed			11,000,000
Litigation settlement upheld			$ 11,000,000
Indemnification liability								$ 0
Purchase Commitment [Member] | Access Capacity on Future Projects Concentration Risk [Member]
Commitments And Contingencies [Line Items]
Concentration percentage						38.00%
Arkansas Royalty Litigation [Member]
Commitments And Contingencies [Line Items]
Number of cases | item							3	3
Arkansas Royalty Litigation [Member] | Arkansas State Court 2010 and 2013 [Member]
Commitments And Contingencies [Line Items]
Number of cases | item							2	2
Arkansas Royalty Litigation [Member] | Federal Court 2014 [Member]
Commitments And Contingencies [Line Items]
Number of cases | item							1	1
Number of alternative damages theories presented | item	2
Loss contingency, range of possible loss, minimum								$ 100,000,000
Arkansas Royalty Litigation [Member] | Arkansas State Court 2015 [Member]
Commitments And Contingencies [Line Items]
Number of cases | item		3
Number of plaintiffs | plaintiff		248
Exploration and Production [Member] | Pressure Pumping Equipment [Member]
Commitments And Contingencies [Line Items]
Number of leases | item							14	14
Aggregate annual lease payment								$ 8,000,000
Exploration and Production [Member] | Drilling Rigs [Member]
Commitments And Contingencies [Line Items]
Number of leases | item							7	7
Lease expiration date						Dec. 31, 2020
Aggregate annual lease payment								$ 13,000,000
Exploration and Production [Member] | Maximum [Member] | Pressure Pumping Equipment [Member]
Commitments And Contingencies [Line Items]
Lease expiration date						Mar. 01, 2018
Exploration and Production [Member] | Minimum [Member] | Pressure Pumping Equipment [Member]
Commitments And Contingencies [Line Items]
Lease expiration date						Dec. 01, 2017
Midstream Services and E&P [Member]
Commitments And Contingencies [Line Items]
Operating leases, future minimum payments, 2016								21,000,000
Operating leases, future minimum payments, 2017								14,000,000
Operating leases, future minimum payments, 2018								8,000,000
Operating leases, future minimum payments, 2019								5,000,000
Operating leases, future minimum payments, 2020								1,000,000
Exploration Program in Canada [Member]
Commitments And Contingencies [Line Items]
Investment in New Brunswick towards Company's commitment							CAD 45	$ 44,000,000
Unrecorded capital investments obligation, Exploration program acres coverage (acres) | a									2.5
Unrecorded capital investments obligation | CAD									CAD 47
Unrecorded promissory note payable | CAD									CAD 45