Pension Plans - Contributions (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 29, 2018	Dec. 31, 2017
Qualified Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Contributions paid-to-date	$ 20.0	$ 10.0
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans
Contributions paid-to-date	0.3	$ 3.1
Expected future contributions	$ 0.6

Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920

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Amount of payment for pension and other postretirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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