Benefit Plans - Changes in benefit obligations (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension benefits
Change in benefit obligation
Benefit obligation, beginning of year	$ 6,815	$ 6,591
Service cost	110	111	$ 113
Interest cost	255	254	286
Participant contributions	0	0
Actuarial (gain) loss	255	(406)
Benefits paid	(646)	(553)
Translation adjustment and other	(55)	6
Benefit obligation, end of year	6,224	6,815	6,591
Change in pension plan assets
Fair value of plan assets, beginning of year	6,284	5,650
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(300)	1,051
Employer contribution	16	131
Benefits paid	(646)	(553)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	(55)	5
Funded status	(925)	(531)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	(198)	(254)
Fair value of plan assets, end of year	$ 5,299	6,284	5,650
Percentage of underfunded status relating to the primary employee plans	78.00%
Postretirement benefits
Change in benefit obligation
Benefit obligation, beginning of year	$ 386	373
Service cost	7	8	9
Interest cost	15	15	18
Participant contributions	13	12
Actuarial (gain) loss	4	(8)
Benefits paid	(35)	(35)
Translation adjustment and other	(7)	5
Benefit obligation, end of year	375	386	$ 373
Change in pension plan assets
Employer contribution	22	23
Funded status	(375)	(386)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	$ (16)	$ (37)

This element represents the percentage of the underfunded status that relates to the primary employee plans.

No definition available.

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- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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- Definition

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

+ References

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- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

+ References

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- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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- Definition

Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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- Definition

Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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- Definition

Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

+ References

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- Definition

Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

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- Definition

Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) plan assets of defined benefit plan.

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- Definition

Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

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