Employee Retirement Plans (Domestic Defined Benefit Plan Assets) (Details) - Pension Benefits [Member] - United States [Member] - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Equity Securities [Member] | U.S. Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 363	$ 374
Equity Securities [Member] | U.S. Companies [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2	57
Equity Securities [Member] | U.S. Companies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		361	317
Equity Securities [Member] | International Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		324	420
Equity Securities [Member] | International Companies [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			117
Equity Securities [Member] | International Companies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		324	303
Fixed Income Securities [Member] | U.S. Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,626	1,815
Fixed Income Securities [Member] | U.S. Companies [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		183	197
Fixed Income Securities [Member] | U.S. Companies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,443	1,618
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	82	105
Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	82	105
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	148	147
Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	148	147
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		199	21
Cash Equivalents [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		199	21
Commodity Option [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]		122
Commodity Option [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]		122
Defined Benefit Plans Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,742	3,004
Defined Benefit Plans Assets [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		384	392
Defined Benefit Plans Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,128	2,360
Defined Benefit Plans Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 230	$ 252

[1] This category includes venture capital, leverage buyouts and distressed debt limited partnerships invested primarily in U.S. companies. The inputs are valued by discounted cash flow analysis and comparable sale analysis.

[2] This category includes industrial, office, apartments, hotels, infrastructure and retail investments which are limited partnerships predominately in the U.S. The inputs are valued by discounted cash flow analysis; comparable sale analysis and periodic external appraisals.

[3] This category includes investments in energy, industrial metals, precious metals, agricultural and livestock primarily through futures, options, swaps and exchange traded funds.