Pension and Other Postretirement Benefit Plans - Summary of Changes in Fair Value of Company's Level 3 Pension Plan Assets (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	$ 826
Actual return on plan assets:
Fair value of plan assets December 31	860	$ 826
United States
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	9,648	10,896
Actual return on plan assets:
Fair value of plan assets December 31	11,361	9,648
United States \| Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	13
Actual return on plan assets:
Fair value of plan assets December 31	9	13
United States \| Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	13	15
Actual return on plan assets:
Relating to assets still held at December 31	(8)	(3)
Relating to assets sold during the year	8	4
Purchases and sales, net	(4)	(3)
Fair value of plan assets December 31	9	13
United States \| Level 3 \| Insurance Contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	0	0
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Relating to assets sold during the year	0	0
Purchases and sales, net	0	0
Fair value of plan assets December 31	0	0
United States \| Level 3 \| Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	0	0
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Relating to assets sold during the year	0	0
Purchases and sales, net	0	0
Fair value of plan assets December 31	0	0
United States \| Level 3 \| Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	13	15
Actual return on plan assets:
Relating to assets still held at December 31	(8)	(3)
Relating to assets sold during the year	8	4
Purchases and sales, net	(4)	(3)
Fair value of plan assets December 31	9	13
International
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	8,580	9,339
Actual return on plan assets:
Fair value of plan assets December 31	10,163	8,580
International \| Insurance Contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	877
Actual return on plan assets:
Fair value of plan assets December 31	916	877
International \| Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	2
Actual return on plan assets:
Fair value of plan assets December 31	1	2
International \| Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	18
Actual return on plan assets:
Fair value of plan assets December 31	21	18
International \| Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	813	473
Actual return on plan assets:
Relating to assets still held at December 31	54	(32)
Purchases and sales, net	(16)	379
Transfers out of Level 3	0	(7)
Fair value of plan assets December 31	851	813
International \| Level 3 \| Insurance Contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	811	470
Actual return on plan assets:
Relating to assets still held at December 31	54	(32)
Purchases and sales, net	(14)	380
Transfers out of Level 3	0	(7)
Fair value of plan assets December 31	851	811
International \| Level 3 \| Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	1	2
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Purchases and sales, net	(1)	(1)
Transfers out of Level 3	0	0
Fair value of plan assets December 31	0	1
International \| Level 3 \| Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	1	1
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Purchases and sales, net	(1)	0
Transfers out of Level 3	0	0
Fair value of plan assets December 31	$ 0	$ 1

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

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Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

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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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- 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.

+ References

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- Definition

Amount, measured using unobservable input, of increase (decrease) in plan asset of defined benefit plan from purchase, sale and settlement of trade associated with underlying investment.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

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