Post-Employment Benefits - Defined Benefit Pension Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total assets measured at NAV	$ 4,265	$ 3,278
Fair value of plan assets	7,116	5,637
U.S. Large Cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	884	719	[1]
U.S. mid cap
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	138	67	[2]
International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	349	226	[3]
U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	149	140	[4]
Corporate debt instruments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	372	385	[4]
Non-U.S. government securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	202	175	[4]
Other fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	320	232	[4]
Absolute return funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	296	261	[5]
Real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	9	7
Other real assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	132	147	[6]
Total
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	2,851	2,359
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	884	719	[1]
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	138	67	[2]
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	349	226	[3]
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	21	[4]
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	112	123	[4]
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	84	48	[4]
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	318	225	[4]
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	4	3	[5]
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	9	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	132	147	[6]
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	2,051	1,586
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	[1]
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	[2]
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	[3]
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	128	119	[4]
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	260	262	[4]
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	118	127	[4]
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	2	7	[4]
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	292	258	[5]
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	[6]
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	800	773
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	[1]
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	[2]
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	[3]
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	[4]
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	[4]
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	[4]
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	[4]
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	[5]
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	[6]
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

[1] A mix of index funds and actively managed equity accounts that are benchmarked to various large cap indices.

[2] A mix of index funds and actively managed equity accounts that are benchmarked to various mid cap indices.

[3] A mix of index funds and actively managed equity accounts that are benchmarked to various non-U.S. equity indices in both developed and emerging markets.

[4] Securities held by actively managed accounts, index funds and mutual funds.

[5] Primarily funds having global mandates with the flexibility to allocate capital broadly across a wide range of asset classes and strategies, including but not limited to equities, fixed income, commodities, financial futures, currencies and other securities, with objectives to outperform agreed upon benchmarks of specific return and volatility targets.

[6] Investments in cash and cash equivalents.