Retirement and Postretirement Plans - Schedule of Plans' Benefit Obligations Determined Using Assumptions (Details)	Dec. 31, 2017
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Compensation increase rate	3.00%
Minimum [Member] \| Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.39%
Minimum [Member] \| OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.30%
Maximum [Member] \| Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.51%
Maximum [Member] \| OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.53%

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

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

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.

+ References

No definition available.

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