Pension and Other Post Retirement Benefit Plans - Schedule of Plan Assets by Category (Details)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	100.00%	100.00%
Target (as a percent)	100.00%	100.00%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	6.00%	4.50%
Target (as a percent)	3.00%	3.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	52.40%	55.80%
Target (as a percent)	55.00%	55.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	39.60%	37.70%
Target (as a percent)	40.00%	40.00%
Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	2.00%	2.00%
Target (as a percent)	2.00%	2.00%

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.

No definition available.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one 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 (d)(5)(i)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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