Financial Instruments and Risk Management - Fair Value (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Fair Value Measurements
Total current derivative contracts, assets	$ 165	$ 21
Total noncurrent derivative contracts, assets	8	3
Total current derivative contracts, liabilities	326	50
Total noncurrent derivative contracts, liabilities	$ 22	31
Discount factor	12 month LIBOR
Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	$ 22	10
Total noncurrent derivative contracts, assets	5	1
Total current derivative contracts, liabilities	36	17
Total noncurrent derivative contracts, liabilities	4	8
Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	143	8
Total noncurrent derivative contracts, assets	3
Total current derivative contracts, liabilities	287	33
Interest rate and other contracts
Fair Value Measurements
Total current derivative contracts, assets		3
Total noncurrent derivative contracts, assets		2
Total current derivative contracts, liabilities	3
Total noncurrent derivative contracts, liabilities	18	23
Derivatives Designated As Hedging Instruments
Fair Value Measurements
Total current derivative contracts, assets	13	8
Total noncurrent derivative contracts, assets	2	1
Total current derivative contracts, liabilities	11	12
Total noncurrent derivative contracts, liabilities	6	8
Derivatives Designated As Hedging Instruments | Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	12	6
Total noncurrent derivative contracts, assets	2	1
Total current derivative contracts, liabilities	9	12
Total noncurrent derivative contracts, liabilities		8
Derivatives Designated As Hedging Instruments | Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	1	2
Total current derivative contracts, liabilities	2
Derivatives Designated As Hedging Instruments | Interest rate and other contracts
Fair Value Measurements
Total noncurrent derivative contracts, liabilities	6
Derivatives Not Designated As Hedging Instruments
Fair Value Measurements
Total current derivative contracts, assets	152	13
Total noncurrent derivative contracts, assets	6	2
Total current derivative contracts, liabilities	315	38
Total noncurrent derivative contracts, liabilities	16	23
Derivatives Not Designated As Hedging Instruments | Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	10	4
Total noncurrent derivative contracts, assets	3
Total current derivative contracts, liabilities	27	5
Total noncurrent derivative contracts, liabilities	4
Derivatives Not Designated As Hedging Instruments | Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	142	6
Total noncurrent derivative contracts, assets	3
Total current derivative contracts, liabilities	285	33
Derivatives Not Designated As Hedging Instruments | Interest rate and other contracts
Fair Value Measurements
Total current derivative contracts, assets		3
Total noncurrent derivative contracts, assets		2
Total current derivative contracts, liabilities	3
Total noncurrent derivative contracts, liabilities	$ 12	$ 23