Financial Instruments and Risk Management - Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value Measurements
Total current derivative contracts, assets	$ 45	$ 40
Total noncurrent derivative contracts, assets	6	46
Total current derivative contracts, liabilities	39	25
Total noncurrent derivative contracts, liabilities	40
Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	31	18
Total noncurrent derivative contracts, assets	6	7
Total current derivative contracts, liabilities	8	3
Total noncurrent derivative contracts, liabilities	1
Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	11	1
Total current derivative contracts, liabilities	31	22
Interest rate and other contracts
Fair Value Measurements
Total current derivative contracts, assets	3	21
Total noncurrent derivative contracts, assets		39
Total noncurrent derivative contracts, liabilities	39
Derivatives Designated As Hedging Instruments
Fair Value Measurements
Total current derivative contracts, assets	31	18
Total noncurrent derivative contracts, assets	6	46
Total current derivative contracts, liabilities	6	3
Total noncurrent derivative contracts, liabilities	40
Derivatives Designated As Hedging Instruments | Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	29	17
Total noncurrent derivative contracts, assets	6	7
Total current derivative contracts, liabilities	6	3
Total noncurrent derivative contracts, liabilities	1
Derivatives Designated As Hedging Instruments | Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	2	1
Derivatives Designated As Hedging Instruments | Interest rate and other contracts
Fair Value Measurements
Total noncurrent derivative contracts, assets		39
Total noncurrent derivative contracts, liabilities	39
Derivatives Not Designated As Hedging Instruments
Fair Value Measurements
Total current derivative contracts, assets	14	22
Total current derivative contracts, liabilities	33	22
Derivatives Not Designated As Hedging Instruments | Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	2	1
Total current derivative contracts, liabilities	2
Derivatives Not Designated As Hedging Instruments | Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	9
Total current derivative contracts, liabilities	31	22
Derivatives Not Designated As Hedging Instruments | Interest rate and other contracts
Fair Value Measurements
Total current derivative contracts, assets	$ 3	$ 21