Retirement Plans (Assumptions Used To Determine Our Benefit Obligations And Net Periodic Benefit Costs) (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Compensation And Retirement Disclosure Line Items
Benefit obligation discount rate	3.62%	4.19%
Rate of increase in compensation levels	2.82%	2.92%
Healthcare cost trend rate:
Weighted average used to determine net cost for the year ended, Discount rate	4.19%	4.46%	4.10%
Weighted averaged used to determine net cost for the year ended, Discount rate for service cost	4.13%	4.42%
Weighted averaged used to determine net cost for the year ended, Discount rate for interest cost	3.56%	3.71%
Weighted average used to determine net cost for the year ended, expected long-term rate of return on assets	7.43%	8.14%	8.15%
Weighed average rate of increase in compensation levels	2.90%	3.39%	3.43%
Other Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Benefit obligation discount rate	3.64%	4.11%
Healthcare cost trend rate:
Trend rate for next year	6.50%	6.50%
Ultimate trend rate	5.00%	5.00%
Year rate reaches ultimate trend rate	2024	2024
Weighted average used to determine net cost for the year ended, Discount rate	4.11%	4.35%	4.03%
Weighted averaged used to determine net cost for the year ended, Discount rate for service cost	4.34%	4.52%
Weighted averaged used to determine net cost for the year ended, Discount rate for interest cost	3.43%	3.53%
Weighted average used to determine net cost for the year ended, expected long-term rate of return on assets	7.76%	7.81%	8.03%

Compensation And Retirement Disclosure Line Items

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- Definition

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate for Interest Cost

+ References

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- Definition

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate for Service Cost

+ References

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

+ 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 (k)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ 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 (k)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

+ References

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ 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 (k)(3)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ 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 (k)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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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

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- Definition

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

+ 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

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- Definition

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

+ 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

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