Financial Instruments and Risk Management - Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value Measurements
Total current derivative contracts, assets	$ 32	$ 36
Total noncurrent derivative contracts, assets	2
Total current derivative contracts, liabilities	34	62
Total noncurrent derivative contracts, liabilities	27	64
Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	7	10
Total noncurrent derivative contracts, assets	2
Total current derivative contracts, liabilities	33	53
Total noncurrent derivative contracts, liabilities		2
Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	22	21
Total current derivative contracts, liabilities	1	6
Cross-currency and other contracts
Fair Value Measurements
Total current derivative contracts, assets	3	5
Total current derivative contracts, liabilities		3
Total noncurrent derivative contracts, liabilities	27	62
Derivatives Designated As Hedging Instruments
Fair Value Measurements
Total current derivative contracts, assets	8	9
Total noncurrent derivative contracts, assets	2
Total current derivative contracts, liabilities	29	45
Total noncurrent derivative contracts, liabilities	27	64
Derivatives Designated As Hedging Instruments | Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets	7	9
Total noncurrent derivative contracts, assets	2
Total current derivative contracts, liabilities	29	42
Total noncurrent derivative contracts, liabilities		2
Derivatives Designated As Hedging Instruments | Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	1
Total current derivative contracts, liabilities		2
Derivatives Designated As Hedging Instruments | Cross-currency and other contracts
Fair Value Measurements
Total current derivative contracts, liabilities		1
Total noncurrent derivative contracts, liabilities	27	62
Derivatives Not Designated as Hedging Instruments
Fair Value Measurements
Total current derivative contracts, assets	24	27
Total current derivative contracts, liabilities	5	17
Derivatives Not Designated as Hedging Instruments | Commodity contracts
Fair Value Measurements
Total current derivative contracts, assets		1
Total current derivative contracts, liabilities	4	11
Derivatives Not Designated as Hedging Instruments | Foreign currency contracts
Fair Value Measurements
Total current derivative contracts, assets	21	21
Total current derivative contracts, liabilities	1	4
Derivatives Not Designated as Hedging Instruments | Cross-currency and other contracts
Fair Value Measurements
Total current derivative contracts, assets	$ 3	5
Total current derivative contracts, liabilities		$ 2