Pension, Other Postretirement Benefits and Savings Plans - Fair Values of Pension Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
United States
Defined Benefit Plan Disclosure [Line Items]
Plan assets, fair value	$ 3,847	$ 3,803
Total plan assets, fair value	4,978	4,972
United States | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	39	58
United States | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	3,805	3,743
United States | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	3	2
United States | Cash and Short Term Securities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	55	62
United States | Cash and Short Term Securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	39	58
United States | Cash and Short Term Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	16	4
United States | Cash and Short Term Securities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Non-U.S. Companies
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Non-U.S. Companies | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Non-U.S. Companies | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Non-U.S. Companies | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	54	38
Total plan assets, fair value	0	0
United States | Equity Securities, Commingled Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Commingled Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Commingled Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	0	0
Total plan assets, fair value	0	0
United States | Equity Securities, Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Mutual Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Mutual Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Equity Securities, Partnership Interests
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	238	263
United States | Debt Securities, Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2,699	2,707
United States | Debt Securities, Corporate Bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2,698	2,707
United States | Debt Securities, Corporate Bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	1	0
United States | Debt Securities, Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	1,033	968
United States | Debt Securities, Government Bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Government Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	1,033	968
United States | Debt Securities, Government Bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Repurchase Agreements
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Repurchase Agreements | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Repurchase Agreements | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Repurchase Agreements | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Asset Backed Securities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	58	63
United States | Debt Securities, Asset Backed Securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Asset Backed Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	58	63
United States | Debt Securities, Asset Backed Securities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	682	697
Total plan assets, fair value	0	0
United States | Debt Securities, Commingled Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Commingled Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Commingled Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	111	123
Total plan assets, fair value	0	0
United States | Debt Securities, Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Mutual Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Debt Securities, Mutual Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Short Term Securities, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	67	87
United States | Alternatives, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	0	0
United States | Alternatives, Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value		0
Total plan assets, fair value	0	0
United States | Alternatives, Real Estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Alternatives, Real Estate | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Alternatives, Real Estate | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Alternatives, Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2	2
United States | Alternatives, Insurance Contracts | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Alternatives, Insurance Contracts | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Alternatives, Insurance Contracts | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2	2
United States | Alternatives, Other Investments
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	1
United States | Alternatives, Other Investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Alternatives, Other Investments | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	1
United States | Alternatives, Other Investments | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
United States | Total Investments
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	4,999	5,011
United States | Other
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	(21)	(39)
Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets, fair value	2,044	1,836
Total plan assets, fair value	2,806	2,507
Non-U.S. | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	163	152
Non-U.S. | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	1,725	1,488
Non-U.S. | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	156	196
Non-U.S. | Cash and Short Term Securities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	20	24
Non-U.S. | Cash and Short Term Securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	19	23
Non-U.S. | Cash and Short Term Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	1	1
Non-U.S. | Cash and Short Term Securities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Equity Securities, Non-U.S. Companies
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	24	20
Non-U.S. | Equity Securities, Non-U.S. Companies | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	24	20
Non-U.S. | Equity Securities, Non-U.S. Companies | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Equity Securities, Non-U.S. Companies | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Equity Securities, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	66	59
Total plan assets, fair value	148	134
Non-U.S. | Equity Securities, Commingled Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	17	16
Non-U.S. | Equity Securities, Commingled Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Equity Securities, Commingled Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	131	118
Non-U.S. | Equity Securities, Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	18	21
Total plan assets, fair value	5	3
Non-U.S. | Equity Securities, Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	5	3
Non-U.S. | Equity Securities, Mutual Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Equity Securities, Mutual Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Equity Securities, Partnership Interests
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	0	0
Non-U.S. | Debt Securities, Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	156	154
Non-U.S. | Debt Securities, Corporate Bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	14	13
Non-U.S. | Debt Securities, Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	142	141
Non-U.S. | Debt Securities, Corporate Bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2,358	2,148
Non-U.S. | Debt Securities, Government Bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	73	68
Non-U.S. | Debt Securities, Government Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2,285	2,080
Non-U.S. | Debt Securities, Government Bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Repurchase Agreements
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	(763)	(777)
Non-U.S. | Debt Securities, Repurchase Agreements | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Repurchase Agreements | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	(763)	(777)
Non-U.S. | Debt Securities, Repurchase Agreements | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Asset Backed Securities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	47	30
Non-U.S. | Debt Securities, Asset Backed Securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	4	2
Non-U.S. | Debt Securities, Asset Backed Securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	43	28
Non-U.S. | Debt Securities, Asset Backed Securities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	579	471
Total plan assets, fair value	10	9
Non-U.S. | Debt Securities, Commingled Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Commingled Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	10	9
Non-U.S. | Debt Securities, Commingled Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	7	5
Total plan assets, fair value	7	5
Non-U.S. | Debt Securities, Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	7	5
Non-U.S. | Debt Securities, Mutual Funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Debt Securities, Mutual Funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Short Term Securities, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	6	2
Non-U.S. | Alternatives, Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	95	154
Non-U.S. | Alternatives, Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value		59
Total plan assets, fair value	4	62
Non-U.S. | Alternatives, Real Estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Alternatives, Real Estate | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	1
Non-U.S. | Alternatives, Real Estate | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	4	61
Non-U.S. | Alternatives, Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	18	14
Non-U.S. | Alternatives, Insurance Contracts | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Alternatives, Insurance Contracts | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	0
Non-U.S. | Alternatives, Insurance Contracts | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	18	14
Non-U.S. | Alternatives, Other Investments
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	10	10
Non-U.S. | Alternatives, Other Investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	0	2
Non-U.S. | Alternatives, Other Investments | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	7	5
Non-U.S. | Alternatives, Other Investments | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	3	3
Non-U.S. | Total Investments
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	2,815	2,607
Non-U.S. | Other
Defined Benefit Plan Disclosure [Line Items]
Total plan assets, fair value	$ (9)	$ (100)