Investments Schedule of Investments (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	0.00%
Investments	$ 636	$ 728
FTS International, Inc.
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	30.00%
Equity Method Investments	329	298
Chaparral Energy, Inc.
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Equity Method Investments	139	141
Sundrop Fuels, Inc.
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	101	111
Clean Energy Fuels Corp.
Schedule of Equity Method Investments [Line Items]
Cost method percentage approximate owned	0.00%
Fair Value Method Investment Ownership Percentage	1.00%
Cost Method Investments	0	100
Fair Value Method Investments	13	12
Twin Eagle Resources Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	30.00%
Equity Method Investments	30	34
Maalt Specialized Bulk, LLC
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%
Equity Method Investments	13	13
Gastar Exploration Ltd.
Schedule of Equity Method Investments [Line Items]
Fair Value Method Investment Ownership Percentage	0.00%
Fair Value Method Investments	0	8
Other Investment Companies [Member]
Schedule of Equity Method Investments [Line Items]
Cost Method Investments	$ 11	$ 11