Post-Employment Benefits - Defined Benefit Pension Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total assets measured at NAV	$ 3,278	$ 3,684
Fair value of plan assets	5,637	5,399
U.S. Large Cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	719	597
U.S. mid cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	67	74
International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	226	63
U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	140	110
Corporate debt instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	385	238
Non-U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	175	59
Other fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	232	265
Absolute return funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	261	262
Real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	7	7
Other real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	147	40
Total
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	2,359	1,715
Quoted prices in active markets for identical assets (Level 1) | U.S. Large Cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	719	597
Quoted prices in active markets for identical assets (Level 1) | U.S. mid cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	67	74
Quoted prices in active markets for identical assets (Level 1) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	226	63
Quoted prices in active markets for identical assets (Level 1) | U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	21	6
Quoted prices in active markets for identical assets (Level 1) | Corporate debt instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	123	132
Quoted prices in active markets for identical assets (Level 1) | Non-U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	48	25
Quoted prices in active markets for identical assets (Level 1) | Other fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	225	260
Quoted prices in active markets for identical assets (Level 1) | Absolute return funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	3	4
Quoted prices in active markets for identical assets (Level 1) | Real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	7	7
Quoted prices in active markets for identical assets (Level 1) | Other real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	147	40
Quoted prices in active markets for identical assets (Level 1) | Total
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	1,586	1,208
Significant other observable inputs (Level 2) | U.S. Large Cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant other observable inputs (Level 2) | U.S. mid cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant other observable inputs (Level 2) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant other observable inputs (Level 2) | U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	119	104
Significant other observable inputs (Level 2) | Corporate debt instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	262	106
Significant other observable inputs (Level 2) | Non-U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	127	34
Significant other observable inputs (Level 2) | Other fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	7	5
Significant other observable inputs (Level 2) | Absolute return funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	258	258
Significant other observable inputs (Level 2) | Real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant other observable inputs (Level 2) | Other real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant other observable inputs (Level 2) | Total
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	773	507
Significant unobservable Inputs (Level 3) | U.S. Large Cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | U.S. mid cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Corporate debt instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Non-U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Other fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Absolute return funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Other real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
Significant unobservable Inputs (Level 3) | Total
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	$ 0	$ 0