Employee Benefit Plans (One Percent Change in Assumed Healthcare Cost Trend Rates) (Details) - Other Postretirement Benefits - U.S. Plans $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
One-percentage point change in assumed healthcare cost trend rates [Abstract]
Effect on total of service and interest costs components, one percent increase	$ 9
Effect on total of service and interest costs components, one percent decrease	(8)
Effect of accumulated postretirement benefit obligations, one percent increase	186
Effect of accumulated postretirement benefit obligations, one percent decrease	$ (154)

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- Definition

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

+ 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 (m)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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- Definition

Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.

+ References

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- Definition

Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

+ References

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- Definition

Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate.

+ References

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