v2.4.0.8
Fair Value Measurement - FV Hierarchy (Details) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2013
Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Deferred compensation investments $ 299 $ 305
Commodity derivatives - assets, gross 1,234 1,637
Total assets 1,533 1,942
Commodity derivatives - liabilities, gross 1,264 1,602
Total liabilities 1,264 1,602
Level 1 [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Deferred compensation investments 299 305
Commodity derivatives - assets, gross 903 1,052
Total assets 1,202 1,357
Commodity derivatives - liabilities, gross 928 1,031
Total liabilities 928 1,031
Level 2 [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Commodity derivatives - assets, gross 316 567
Total assets 316 567
Commodity derivatives - liabilities, gross 334 567
Total liabilities 334 567
Level 3 [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Commodity derivatives - assets, gross 15 18
Total assets 15 18
Commodity derivatives - liabilities, gross 2 4
Total liabilities $ 2 $ 4