Retirement and Postretirement Plans - Schedule of Funded Status of Plans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 17, 2017
Pension Benefits [Member]
Amounts recorded in the balance sheet:
Current liabilities	$ (3,714)
Noncurrent liabilities	(75,693)	$ (108,000)
Funded status	(79,407)
OPEB [Member]
Amounts recorded in the balance sheet:
Current liabilities	(1,882)
Noncurrent liabilities	(21,492)	$ (22,600)
Funded status	$ (23,374)

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(15))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant