Benefit Plans - Reconciliation of Benefit Obligations and Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation:
Actuarial (gain) loss	$ (212)	$ 100
Pension Benefits [Member]
Change in benefit obligation:
Benefit obligation, beginning balance	3,242	3,131
Acquisitions		103
Service cost	8	8	$ 8
Interest cost	110	119	128
Service cost	8	8	8
Interest cost	110	119	128
Acquisitions		103
Amendments	0	0
Actuarial (gain) loss	(212)	100
Benefits paid from plan assets	(187)	(192)
Settlements	(35)	(37)
Foreign exchange	(7)	10
Benefit obligation, ending balance	2,919	3,242	3,131
Benefit obligation, ending balance	2,919	3,242	3,131
Settlements	(35)	(37)
Foreign exchange	(7)	10
Change in plan assets:
Fair value of plan assets at January 1	2,577	2,423
Acquisitions		75
Actual return on plan assets	(83)	247
Company contributions	39	51
Benefits paid from plan assets	(187)	(192)
Actual return on plan assets	(83)	247
Company contributions	39	51
Acquisitions		75
Benefits paid from plan assets	(187)	(192)
Settlements	(35)	(37)
Foreign exchange	(7)	10
Fair value of plan assets, ending balance	2,304	2,577	2,423
Funded status	(615)	(665)
Fair value of plan assets, ending balance	2,304	2,577	2,423
Funded status	(615)	(665)
Other Postretirement Benefits [Member]
Change in benefit obligation:
Benefit obligation, beginning balance	62	66
Service cost	1	1	1
Interest cost	2	2	3
Plan participants' contributions	4	5
Service cost	1	1	1
Interest cost	2	2	3
Amendments	0	0
Actuarial (gain) loss	(6)	(1)
Benefits paid from plan assets	(10)	(11)
Benefit obligation, ending balance	53	62	66
Benefit obligation, ending balance	53	62	66
Change in plan assets:
Fair value of plan assets at January 1	88	86
Actual return on plan assets		5
Company contributions	3	3
Plan participants' contributions	4	5
Benefits paid from plan assets	(10)	(11)
Actual return on plan assets		5
Company contributions	3	3
Benefits paid from plan assets	(10)	(11)
Fair value of plan assets, ending balance	85	88	86
Funded status	32	26
Fair value of plan assets, ending balance	85	88	$ 86
Funded status	$ 32	$ 26

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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Amount of increase in benefit obligation of defined benefit plan from business combination.

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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 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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