Retirement Benefits Plans - Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	$ 4,447	$ 4,406
United States pension plans percentage of worldwide pension assets	67.00%
United Kingdom pension plans percentage of worldwide pension assets	27.00%
United States pension plans' target allocation of United States equities	33.00%
United States pension plans' target allocation of non-United States equities	32.00%
United States pension plans' target allocation of real estate	8.00%
United State pension plans' target allocation of debt securities	22.00%
United States pension plans' target allocation of other, including hedge funds and cash equivalents	5.00%
United Kingdom pension plans' target allocation of equities	57.00%
Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	$ 498	513
Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	1,707	1,646
Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	101	93
Hedge Funds, Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	85	92
Non-United States Equity and Global Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	413	415
Non-United States Equity and Global Equities [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		0
Non-United States Equity and Global Equities [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	413	415
Non-United States Equity and Global Equities [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0
United States Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	94	96
United States Equity [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
United States Equity [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	94	96
United States Equity [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0
Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	422	418
Fixed Income [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Fixed Income [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	422	418
Fixed Income [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	359	357
Fixed Income Securities [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Fixed Income Securities [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	359	357
Fixed Income Securities [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
United States treasuries [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	123	105
United States treasuries [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	123	105
United States treasuries [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
United States treasuries [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Bank Loans [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	150	136
Bank Loans [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Bank Loans [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	150	136
Bank Loans [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Real Estate Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	201	251
Real Estate Securities [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	195	244
Real Estate Securities [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Real Estate Securities [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	6	7
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	104	98
Equity Securities [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	104	98
Equity Securities [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Equity Securities [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	276	227
Cash Equivalents [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	21	17
Cash Equivalents [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	255	210
Cash Equivalents [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Exchange Traded Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	55	49
Exchange Traded Funds [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	55	49
Exchange Traded Funds [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Exchange Traded Funds [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Other Pension Plan Asset [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	109	100
Other Pension Plan Asset [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	0	0
Other Pension Plan Asset [Member] | Other observable inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	14	14
Other Pension Plan Asset [Member] | Unobservable inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	95	86
Fair Value, Concentration of Risk, Market Risk Management, Effects on Income or Net Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	2,038	2,043
Money Market Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	$ 18	$ 19