Summary of Recognized Settlement Loss by Quarter (Detail) - USD ($) $ in Thousands	3 Months Ended	4 Months Ended	9 Months Ended
Oct. 06, 2018	Jul. 14, 2018	Oct. 07, 2017	Apr. 21, 2018	Oct. 06, 2018	Oct. 07, 2017
Pension And Other Postretirement Benefit Expense [Abstract]
Settlement loss	$ 930	$ 1,035	$ 3,030	$ 4,668	$ 6,633	$ 3,030

Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(7)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)(7)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920

Name:	us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration