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Employee Benefit Plans Employee Benefit Plans 11 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Healthcare Cost Trend Rate
Initial health care cost for employees under age of 65 (as a percent)	6.10%
Ultimate health care cost for employees under age of 65 (as a percent)	4.60%
Initial Health care cost for employees of age 65 and over (as a percent)	5.10%
Ultimate health care cost for employees of age 65 and over (as a percent)	4.20%
Effects of one-percentage-point change in assumed health care cost trend rates
Effect on total of service and interest cost components -1 Percentage Point Increase	$ 41
Effect on total of service and interest cost components -1 Percentage Point Decrease	(35)
Effect on post-retirement benefit obligation -1 Percentage Point Increase	759
Effect on post-retirement benefit obligation -1 Percentage Point Decrease	$ (659)
Union plan
Employee benefit plans
Expected long-term return on plan assets	6.00%	6.00%	7.00%
Non-union plan
Employee benefit plans
Expected long-term return on plan assets	4.20%	4.20%	4.20%

X

- Definition

Represents the initial health care cost for employees of age sixty-five and over.

+ References

No definition available.

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- Definition

Represents the initial health care cost for employees under age of sixty-five.

+ References

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- Definition

The ultimate trend rate for health care costs for employees of age sixty-five and over.

+ References

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The ultimate trend rate for health care costs for employees under age of sixty-five.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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

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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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-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

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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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-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

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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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-Publisher FASB
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-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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