Employee Benefits - Schedule of Fair Value of U.S Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
U.K. and Non-U.S. Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total	$ 5,675	$ 5,903	$ 6,224
U.K. and Non-U.S. Pension Plan | Pooled Funds, Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total	101	85
U.K. and Non-U.S. Pension Plan | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	86	159
U.K. and Non-U.S. Pension Plan | Derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	62	66
U.K. and Non-U.S. Pension Plan | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	10	111
U.K. and Non-U.S. Pension Plan | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	773	717
U.K. and Non-U.S. Pension Plan | Segment Geographical Groups of Countries Group Three [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	135	133
U.K. and Non-U.S. Pension Plan | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	2,129	3,145
U.K. and Non-U.S. Pension Plan | Pooled funds - Global
Defined Benefit Plan Disclosure [Line Items]
Total	365	360
U.K. and Non-U.S. Pension Plan | Pooled funds - Europe
Defined Benefit Plan Disclosure [Line Items]
Total	18	17
U.K. and Non-U.S. Pension Plan | Annuities
Defined Benefit Plan Disclosure [Line Items]
Total	1,773	827
U.K. and Non-U.S. Pension Plan | Pooled funds - Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	223	283
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total	1,947	2,560
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled Funds, Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	86	159
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Segment Geographical Groups of Countries Group Three [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	135	133
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	1,726	2,268
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled funds - Global
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled funds - Europe
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Annuities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled funds - Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total	413	1,054
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Pooled Funds, Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	66
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	10	111
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Segment Geographical Groups of Countries Group Three [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	403	877
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Pooled funds - Global
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Pooled funds - Europe
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Annuities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Pooled funds - Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total	1,773	827
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Pooled Funds, Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Segment Geographical Groups of Countries Group Three [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Pooled funds - Global
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Pooled funds - Europe
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Annuities
Defined Benefit Plan Disclosure [Line Items]
Total	1,773	827	836
U.K. and Non-U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Pooled funds - Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total	1,683	1,951	$ 2,036
U.S. Pension Plan | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	100	33
U.S. Pension Plan | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	268	299
U.S. Pension Plan | Small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	15	30
U.S. Pension Plan | Large cap international
Defined Benefit Plan Disclosure [Line Items]
Total	64	52
U.S. Pension Plan | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	81	203
U.S. Pension Plan | International pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	196	210
U.S. Pension Plan | Pooled funds small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	52	58
U.S. Pension Plan | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	105	148
U.S. Pension Plan | Government and agency bonds
Defined Benefit Plan Disclosure [Line Items]
Total	132	128
U.S. Pension Plan | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Fixed income derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	65	69
U.S. Pension Plan | Corporate Bonds And Pooled Funds
Defined Benefit Plan Disclosure [Line Items]
Total	255	336
U.S. Pension Plan | Commodity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	22	13
U.S. Pension Plan | Real estate and REITS
Defined Benefit Plan Disclosure [Line Items]
Total	61	67
U.S. Pension Plan | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	267	305
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total	727	750
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	100	33
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	268	299
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	15	30
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Large cap international
Defined Benefit Plan Disclosure [Line Items]
Total	64	52
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	78	170
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | International pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled funds small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency bonds
Defined Benefit Plan Disclosure [Line Items]
Total	76	52
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	65	47
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate Bonds And Pooled Funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate and REITS
Defined Benefit Plan Disclosure [Line Items]
Total	61	67
U.S. Pension Plan | Quoted Prices in Active Markets for Identical Assets (Level 1) | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total	186	292
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Large cap international
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	3	33
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | International pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Pooled funds small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	105	148
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Government and agency bonds
Defined Benefit Plan Disclosure [Line Items]
Total	56	76
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Fixed income derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	22
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Corporate Bonds And Pooled Funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Commodity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	22	13
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Real estate and REITS
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Other Observable Inputs (Level 2) | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Large cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Large cap international
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Equity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | International pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Pooled funds small cap domestic
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Government and agency bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Fixed income derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Corporate Bonds And Pooled Funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Commodity derivatives
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Real estate and REITS
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
U.S. Pension Plan | Significant Unobservable Inputs (Level 3) | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Total	$ 0	$ 0