Retirement and Postretirement Plans - Summary of Accumulated Other Comprehensive Income (Loss) Related to Pension and Other Postretirement Benefit Plans (Details) $ in Thousands	11 Months Ended
Dec. 31, 2017 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 9,733
December 31, 2017	9,733
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(1,433)
December 31, 2017	$ (1,433)

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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