Employee Benefit Plans - Change in Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plans Defined Benefit [Member] \| U.S.
Change in Benefit Obligation
Benefit obligation at January 1	$ 2,136	$ 3,236
Service cost	79	83	$ 89
Interest cost	79	99	118
Plan participant contributions	0	0
Plan amendments	0	0
Actuarial (gain) loss	278	(44)
Benefits paid	(253)	(507)
Curtailment	0	(4)
Settlement	0	(730)
Recognition of termination benefits	0	3
Foreign currency exchange rate change	0	0
Benefit obligation at December 31	2,319	2,136	3,236
Change in Fair Value of Plan Assets
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	1,336	2,541
Actual return on plan assets	273	(112)
Company contributions	235	144
Plan participant contributions	0	0
Defined Benefit Plan Plan Assets Benefits Paid	(253)	(507)
Settlement	0	(730)
Foreign currency exchange rate change	0	0
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	1,591	1,336	2,541
Funded Status	(728)	(800)
Pension Plans Defined Benefit [Member] \| Foreign Pension Plans, Defined Benefit [Member]
Change in Benefit Obligation
Benefit obligation at January 1	3,438	3,845
Service cost	69	81	77
Interest cost	97	107	103
Plan participant contributions	2	2
Plan amendments	0	7
Actuarial (gain) loss	387	(259)
Benefits paid	(147)	(143)
Curtailment	(69)	(3)
Settlement	0	0
Recognition of termination benefits	1	0
Foreign currency exchange rate change	102	(199)
Benefit obligation at December 31	3,880	3,438	3,845
Change in Fair Value of Plan Assets
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	3,358	3,647
Actual return on plan assets	529	(106)
Company contributions	464	156
Plan participant contributions	2	2
Defined Benefit Plan Plan Assets Benefits Paid	(147)	(143)
Settlement	0	0
Foreign currency exchange rate change	100	(198)
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	4,306	3,358	3,647
Funded Status	426	(80)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Change in Benefit Obligation
Benefit obligation at January 1	218	265
Service cost	1	1	2
Interest cost	8	8	9
Plan participant contributions	20	22
Plan amendments	0	0
Actuarial (gain) loss	27	(10)
Benefits paid	(59)	(67)
Curtailment	0	0
Settlement	0	0
Recognition of termination benefits	0	0
Foreign currency exchange rate change	1	(1)
Benefit obligation at December 31	216	218	265
Change in Fair Value of Plan Assets
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	0	0
Actual return on plan assets	0	0
Company contributions	39	45
Plan participant contributions	20	22
Defined Benefit Plan Plan Assets Benefits Paid	(59)	(67)
Settlement	0	0
Foreign currency exchange rate change	0	0
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	0	0	$ 0
Funded Status	$ (216)	$ (218)

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.

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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.

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

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

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

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Amount of (increase) decrease in benefit obligation of defined benefit plan from event reducing expected years of future service of present employees or eliminating accrual of benefits for some or all future services of present employees.

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

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

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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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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Amount of contributions received by defined benefit plan from participant which increases plan assets.

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

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

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Amount of (increase) decrease to benefit obligation of defined benefit plan from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Includes, but is not limited to, lump-sum cash payment to participant in exchange for right to receive specified benefits, purchase of nonparticipating annuity contract and change from remeasurement.

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Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

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Amount of increase in benefit obligation for benefits provided to employees payable from defined benefit plan or payable upon retirement.

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