Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Percentage of investment to total investment within defined benefit plan asset category.

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Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Cost for defined contribution retirement plans	$ 70	$ 66	$ 62
Postretirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status of the plan	(41)	(34)
United States
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status of the plan	$ 1	(77)
United States \| Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, target allocation percentage	80.00%
Defined benefit plan, target allocation percentage to hedge projected liabilities	90.00%
United States \| Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, target allocation percentage	20.00%
United States \| U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, target allocation within equity securities	55.00%
United States \| Non-US Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, target allocation within equity securities	45.00%
U.K. Plan
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status of the plan	$ 39	$ 63
Expected long-term rate of return on plan assets	4.85%	4.95%	5.00%
Liability interest rate sensitivity	95.00%
Liability inflation rate sensitivity	105.00%
Employer contributions	$ 3
U.K. Plan \| Matching Assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, target allocation percentage	60.00%
U.K. Plan \| Growth Assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, target allocation percentage	40.00%
Qualified Plan \| United States
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status of the plan	$ 76
Expected long-term rate of return on plan assets	5.80%
Nonqualified Plan \| United States
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status of the plan	$ (75)
Employer contributions	$ 5
Minimum \| Qualified Plan \| United States
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets		3.00%	2.35%
Maximum \| Qualified Plan \| United States
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets		5.40%	5.65%