Divestitures VPP Volumes Produced During Period Table (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Mcfe	Sep. 30, 2012 Mcfe	Sep. 30, 2013 Mcfe	Sep. 30, 2012 Mcfe
Corporate VPP [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	42,300,000,000	51,100,000,000	131,100,000,000	154,700,000,000
Corporate VPP [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	38,000,000,000	44,600,000,000	117,600,000,000	136,100,000,000
Corporate VPP [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	209,900	442,500	668,200	1,316,200
Corporate VPP [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	512,200	661,700	1,591,600	1,777,200
VPP 10 Anadarko Basin Granite Wash [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	6,700,000,000	9,500,000,000	20,900,000,000	24,500,000,000
VPP 10 Anadarko Basin Granite Wash [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	3,700,000,000	5,300,000,000	11,400,000,000	13,500,000,000
VPP 10 Anadarko Basin Granite Wash [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	131,000	206,000	426,000	547,000
VPP 10 Anadarko Basin Granite Wash [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	371,900	503,700	1,158,600	1,286,600
VPP 9 Mid-Continent [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	5,200,000,000	5,800,000,000	16,000,000,000	18,100,000,000
VPP 9 Mid-Continent [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	4,100,000,000	4,500,000,000	12,500,000,000	14,000,000,000
VPP 9 Mid-Continent [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	52,300	60,800	162,500	191,000
VPP 9 Mid-Continent [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	140,300	158,000	433,000	490,600
VPP 8 Barnett Shale [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	16,600,000,000	19,400,000,000	51,600,000,000	61,100,000,000
VPP 8 Barnett Shale [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	16,600,000,000	19,400,000,000	51,600,000,000	61,100,000,000
VPP 8 Barnett Shale [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0	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	0	0
VPP 7 Permian Basin [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)		1,000,000,000		3,400,000,000
VPP 7 Permian Basin [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)		200,000,000		400,000,000
VPP 7 Permian Basin [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)		147,300		490,300
VPP 7 Permian Basin [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	1,400,000,000	3,700,000,000	4,200,000,000
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)	1,200,000,000	1,300,000,000	3,600,000,000	4,100,000,000
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	18,000	18,000
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	0	0
VPP 5 South Texas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	1,900,000,000	2,200,000,000	5,800,000,000	6,900,000,000
VPP 5 South Texas [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	1,900,000,000	2,200,000,000	5,700,000,000	6,800,000,000
VPP 5 South Texas [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	6,700	6,600	19,000	21,200
VPP 5 South Texas [Member] | NGL Reserves
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0	0	0
VPP 4 Anadarko and Arkoma Basins [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	2,600,000,000	3,000,000,000	8,100,000,000	9,300,000,000
VPP 4 Anadarko and Arkoma Basins [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	2,400,000,000	2,900,000,000	7,800,000,000	9,000,000,000
VPP 4 Anadarko and Arkoma Basins [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	13,900	15,800	42,700	48,700
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	0	0
VPP 3 Anadarko Basin [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	2,000,000,000	2,300,000,000	6,200,000,000	7,100,000,000
VPP 3 Anadarko Basin [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	2,000,000,000	2,300,000,000	6,200,000,000	7,100,000,000
VPP 3 Anadarko Basin [Member] | Oil [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	0	0	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	0	0
VPP 2 Texas, Oklahoma and Kansas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	2,600,000,000	2,800,000,000	7,900,000,000	8,600,000,000
VPP 2 Texas, Oklahoma and Kansas [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	2,600,000,000	2,800,000,000	7,900,000,000	8,600,000,000
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	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	0	0
VPP 1 Kentucky and West Virginia [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Reserves (Energy) (Duration)	3,500,000,000	3,700,000,000	10,900,000,000	11,500,000,000
VPP 1 Kentucky and West Virginia [Member] | Natural Gas [Member]
Acquisitions, Divestitures, Joint Ventures, VPP's [Line Items]
Proved Developed and Undeveloped Reserves (Volume)	3,500,000,000	3,700,000,000	10,900,000,000	11,500,000,000
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	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	0	0