Employee Benefit Plans (Schedule of Assumption of Health Care Cost Trend Rates) (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Health Care Cost Trend Rate Assumed for Next Year	8.00%	8.00%
Rate that the Cost Trend Rate Gradually Declines to	5.00%	5.00%
Year that the Rate Reaches the Rate it is Assumed to Remain at	2023	2022

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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