Benefit Obligations Benefit Obligations (Schedule of US Health Care Cost Trend Rates) (Details) - Domestic Plan [Member] - Postretirement Health Coverage [Member]	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ScheduleofHealthCareCostTrend [Line Items]
Health care cost trend rate assumed for next year	9.00%	9.50%	10.00%
Health care cost trend ultimate rate	5.00%	5.00%	5.00%
Health care cost trend ultimate rate year	2026	2026	2026

[Line Items] for Schedule of health care cost trend rate assumptions

No definition available.

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- Definition

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

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

+ Details

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- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

+ Details

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- Definition

Year ultimate health care cost trend rate is expected to be reached, in CCYY format.

+ References

+ Details

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- Details

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- Details

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