Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair value of commodity derivatives
Derivative Assets	$ 239	$ 296
Derivative Liabilities	(347)	(598)
Current Assets
Fair value of commodity derivatives
Derivative Assets	166	160
Noncurrent Assets
Fair value of commodity derivatives
Derivative Assets	73	136
Current Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(111)	(126)
Noncurrent Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(236)	(472)
Commodity contracts | Current Assets
Fair value of commodity derivatives
Derivative Assets	162	153
Commodity contracts | Noncurrent Assets
Fair value of commodity derivatives
Derivative Assets	53	99
Commodity contracts | Current Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(102)	(119)
Commodity contracts | Noncurrent Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(11)	(36)
FTRs | Current Assets
Fair value of commodity derivatives
Derivative Assets	4	7
FTRs | Noncurrent Assets
Fair value of commodity derivatives
Derivative Assets	0	1
FTRs | Current Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(9)	(7)
FTRs | Noncurrent Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(3)	(2)
NUGs | Noncurrent Assets
Fair value of commodity derivatives
Derivative Assets	20	36
NUGs | Noncurrent Liabilities
Fair value of commodity derivatives
Derivative Liabilities	(222)	(290)
LCAPP | Noncurrent Liabilities
Fair value of commodity derivatives
Derivative Liabilities	$ 0	$ (144)