Postretirement Health Care Plans - Net Periodic Postretirement Health Care Cost (Detail) - Postretirement Health Coverage - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Apr. 01, 2017
Postretirement Health Care Plans [Line Items]
Interest cost	$ 0.5	$ 0.5
Expected return on plan assets	(0.2)	(0.2)
Amortization of unrecognized gain	(0.1)	(0.1)
Net periodic pension cost	$ 0.2	$ 0.2

Defined Benefit Plan, Amortization of Unrecognized Gain (Loss)

No definition available.

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Period Type:	duration

- Definition

Postretirement Health Care Plans [Line Items]

+ References

No definition available.

+ Details

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- Definition

Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

+ References

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of net periodic benefit cost (credit) for defined benefit plan.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Details

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