Consolidated and Combined Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Statement of Comprehensive Income [Abstract]
Unrecognized loss on derivatives, tax	$ 0.0	$ (0.3)	$ (0.2)	$ (0.2)
Unrecognized gain (loss) on benefit plans, tax	$ 19.3	$ (30.8)	$ 15.0	$ 2.1

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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