Pension Plans Retirement Benefits and Savings Plans (details) - Future Payments $ in Millions	Dec. 31, 2017 USD ($)
Pension Plans [Member]
Estimated Future Benefit Payments
Benefits expected to be paid, 2018	$ 230
Benefits expected to be paid, 2019	241
Benefits expected to be paid, 2020	245
Benefits expected to be paid, 2021	256
Benefits expected to be paid, 2022	262
Benefits expected to be paid, 2023 through 2027	1,342
Postretirement Benefit Plans [Member]
Estimated Future Benefit Payments
Benefits expected to be paid, 2018	14
Benefits expected to be paid, 2019	14
Benefits expected to be paid, 2020	14
Benefits expected to be paid, 2021	15
Benefits expected to be paid, 2022	15
Benefits expected to be paid, 2023 through 2027	$ 74

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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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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