Natural Gas and Oil Property Divestitures - VPP Volumes Produced During Period Table (Details)	3 Months Ended
	Mar. 31, 2014 Mcfe	Mar. 31, 2013 Mcfe
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	39,400,000,000	44,900,000,000
Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	35,500,000,000	40,500,000,000
Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	182,700	236,400
NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	451,700	526,500
VPP 10 Anadarko Basin Granite Wash [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	5,500,000,000	6,900,000,000
VPP 10 Anadarko Basin Granite Wash [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	2,800,000,000	3,700,000,000
VPP 10 Anadarko Basin Granite Wash [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	109,000	154,000
VPP 10 Anadarko Basin Granite Wash [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	345,200	407,700
VPP 9 Mid-Continent [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	4,900,000,000	5,500,000,000
VPP 9 Mid-Continent [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	4,000,000,000	4,400,000,000
VPP 9 Mid-Continent [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	49,000	56,200
VPP 9 Mid-Continent [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	106,500	118,800
VPP 8 Barnett Shale [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	15,700,000,000	18,000,000,000
VPP 8 Barnett Shale [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	15,700,000,000	18,000,000,000
VPP 8 Barnett Shale [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 8 Barnett Shale [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 6 East Texas and Texas Gulf Coast [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	1,200,000,000	1,200,000,000
VPP 6 East Texas and Texas Gulf Coast [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	1,100,000,000	1,200,000,000
VPP 6 East Texas and Texas Gulf Coast [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	6,000	6,000
VPP 6 East Texas and Texas Gulf Coast [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 5 South Texas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	1,800,000,000	2,000,000,000
VPP 5 South Texas [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	1,700,000,000	2,000,000,000
VPP 5 South Texas [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	6,300	6,000
VPP 5 South Texas [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 4 Anadarko and Arkoma Basins [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	2,400,000,000	2,700,000,000
VPP 4 Anadarko and Arkoma Basins [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	2,300,000,000	2,600,000,000
VPP 4 Anadarko and Arkoma Basins [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	12,400	14,200
VPP 4 Anadarko and Arkoma Basins [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 3 Anadarko Basin [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	1,900,000,000	2,100,000,000
VPP 3 Anadarko Basin [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	1,900,000,000	2,100,000,000
VPP 3 Anadarko Basin [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 3 Anadarko Basin [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 2 Texas, Oklahoma and Kansas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	2,400,000,000	2,700,000,000
VPP 2 Texas, Oklahoma and Kansas [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	2,400,000,000	2,700,000,000
VPP 2 Texas, Oklahoma and Kansas [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 2 Texas, Oklahoma and Kansas [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 1 Kentucky and West Virginia [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	3,600,000,000	3,800,000,000
VPP 1 Kentucky and West Virginia [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	3,600,000,000	3,800,000,000
VPP 1 Kentucky and West Virginia [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0
VPP 1 Kentucky and West Virginia [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0