Employee Benefit Plans - Change in Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($) $ in Millions		12 Months Ended
Dec. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United Kingdom
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		$ 1,305	$ 1,235
Interest cost		28	34	$ 41
Plan amendment		19	0
Actuarial (gain) loss		(62)	(23)
Benefits paid		(56)	(60)
Settlement		0	0
Foreign currency exchange rate changes		(70)	119
Projected benefit obligation at end of year		1,164	1,305	1,235
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year		1,390	1,207
Actual return on plan assets		(35)	109
Employer contributions		3	13
Benefits paid		(56)	(60)
Settlement		0	0
Foreign currency exchange rate changes		(75)	121
Fair value of plan assets at end of year		1,227	1,390	1,207
Qualified Plan \| United States
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		1,743	1,745
Interest cost		57	74	76
Plan amendment		0	0
Actuarial (gain) loss		(142)	128
Benefits paid		(69)	(62)
Settlement		0	(142)
Foreign currency exchange rate changes		0	0
Projected benefit obligation at end of year		1,589	1,743	1,745
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year		1,764	1,700
Actual return on plan assets		(113)	268
Employer contributions		0	0
Benefits paid		(69)	(62)
Settlement	$ (142)	0	(142)
Foreign currency exchange rate changes		0	0
Fair value of plan assets at end of year		1,582	1,764	1,700
Nonqualified Plan \| United States
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year		78	74
Interest cost		2	3	3
Plan amendment		0	0
Actuarial (gain) loss		(5)	6
Benefits paid		(5)	(5)
Settlement		0	0
Foreign currency exchange rate changes		0	0
Projected benefit obligation at end of year		70	78	74
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year		0	0
Actual return on plan assets		0	0
Employer contributions		5	5
Benefits paid		(5)	(5)
Settlement		0	0
Foreign currency exchange rate changes		0	0
Fair value of plan assets at end of year		$ 0	$ 0	$ 0

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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- 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.

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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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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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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 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 foreign currency translation gain (loss) which increases (decreases) plan assets of 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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