|**Accumulated Other Comprehensive Loss, Excluding Noncontrolling Interests (Tables)**         | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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|**Equity [Abstract]**                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Schedule of Changes in Accumulated Other Comprehensive Loss, Net of Tax                       | The following table provides the changes, net of tax, inAccumulated other comprehensive loss:Net Unrealized Gains/(Losses)Benefit Plans(MILLIONS OF DOLLARS)Foreign Currency Translation AdjustmentsDerivative Financial InstrumentsAvailable-For-Sale SecuritiesActuarial Gains/(Losses)Prior Service (Costs)/Credits and OtherAccumulated Other Comprehensive Income/(Loss)Balance, December 31, 2018$(6,075)$167$(68)$(6,027)$728$(11,275)Other comprehensive income/(loss)(a)304—4440(35)353Balance, March 31, 2019$(5,772)$167$(24)$(5,986)$693$(10,923)(a)Amounts do not include foreign currency translation adjustments attributable to noncontrolling interests of$4 millionloss forthe first three months of2019.
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|The following table provides the changes, net of tax, inAccumulated other comprehensive loss:
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|(MILLIONS OF DOLLARS)                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Balance, December 31, 2018                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Other comprehensive income/(loss)(a)                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Balance, March 31, 2019                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|(a)                                                                                           | Amounts do not include foreign currency translation adjustments attributable to noncontrolling interests of$4 millionloss forthe first three months of2019.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

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