Postretirement Health Care Plans - Net Periodic Postretirement Health Care Cost (Detail) - Postretirement Health Coverage - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Postretirement Health Care Plans [Line Items]
Interest cost	$ 0.5	$ 0.4	$ 1.0	$ 0.9
Expected return on plan assets	(0.2)	(0.2)	(0.4)	(0.4)
Amortization of unrecognized gain	(0.2)	(0.1)	(0.4)	(0.2)
Net periodic cost	$ 0.1	$ 0.1	$ 0.2	$ 0.3

Amount of cost recognized for passage of time related to defined benefit plan.

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)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920

Name:	us-gaap_DefinedBenefitPlanInterestCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration