Benefit Plans - Summary of Common/Collective Trust Fund Pension Plan Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 01, 2017
Defined Benefit Plan Disclosure [Line Items]
Total common/collective trust funds	$ 257,790	$ 227,549
Common/Collective Trust Funds - Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total common/collective trust funds	157,290	139,735
Common/Collective Trust Funds - Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Total common/collective trust funds	$ 100,500	$ 87,814

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

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

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