Segment Reporting (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	$ 1,869	$ 1,112	$ 3,464	$ 2,334
Total Revenues	4,675	3,389	8,098	5,807
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	1,009	1,700	1,174	1,694
Total Assets	42,145		42,145		41,611
Exploration and Production
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	2,406	2,117	3,858	3,185
Exploration and Production Revenue	0	0	0	0
Total Revenues	2,406	2,117	3,858	3,185
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	1,162	1,090	625	1,178
Total Assets	37,983		37,983		37,004
Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	3,990	2,274	7,516	4,664
Exploration and Production Revenue	(1,933)	(1,161)	(3,678)	(2,336)
Total Revenues	2,057	1,113	3,838	2,328
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	158	1,089	272	1,156
Total Assets	2,423		2,423		2,291
Oilfield Services
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	582	506	1,127	953
Exploration and Production Revenue	(377)	(347)	(735)	(659)
Total Revenues	205	159	392	294
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	4	57	26	96
Total Assets	1,780		1,780		2,115
Other Operations
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	14	0	23	0
Exploration and Production Revenue	(7)	0	(13)	0
Total Revenues	7	0	10	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(213)	(401)	451	(502)
Total Assets	2,313		2,313		2,529
Intercompany Eliminations
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	(2,317)	(1,508)	(4,426)	(2,995)
Exploration and Production Revenue	2,317	1,508	4,426	2,995
Total Revenues	0	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(102)	(135)	(200)	(234)
Total Assets	(2,354)		(2,354)		(2,328)
Consolidated Entities
Segment Reporting Information [Line Items]
Natural gas, oil and NGL sales	4,675	3,389	8,098	5,807
Exploration and Production Revenue	0	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	1,009	1,700	1,174	1,694
Total Assets	$ 42,145		$ 42,145		$ 41,611