Marketable Securities - Reconciles Cost Basis to Fair Market Value of Company's Equity Security (Detail) (Equity securities, USD $) In Millions, unless otherwise specified	Mar. 28, 2015	Sep. 27, 2014
Equity securities
Schedule Of Marketable Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	$ 16.1	$ 15.5
Gross Unrealized Gains	12.4	10.2
Gross Unrealized Losses	(6.7)	(1.3)
Fair Value	$ 21.8	$ 24.4

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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Balance Type:	debit
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