Employee Benefit Plans - Expected Payments (Details) $ in Millions	Dec. 31, 2018 USD ($)
Postretirement Medical Plan
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	$ 3
2020	3
2021	3
2022	3
2023	3
2024-2028	14
United Kingdom
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	40
2020	41
2021	43
2022	45
2023	46
2024-2028	257
Qualified Plan \| United States
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	80
2020	83
2021	87
2022	89
2023	92
2024-2028	492
Nonqualified Plan \| United States
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	5
2020	5
2021	5
2022	5
2023	5
2024-2028	$ 25

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- Definition

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

+ References

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- Definition

Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

+ References

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Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

+ References

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Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

+ References

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Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

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