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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.

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- Definition Amount of investment within defined benefit plan asset category. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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