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Income Taxes - Activity of Company's Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions | 12 Months Ended
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Sep. 28, 2019 | Sep. 29, 2018
Income Tax Disclosure [Abstract] |  |
Balance at beginning of fiscal year | $ 89.5 | $ 90.3
Tax positions related to current year: |  |
Additions | 22.7 | 9.0
Reductions | 0.0 | 0.0
Tax positions related to prior years: |  |
Additions related to change in estimate | 0.0 | 6.6
Reductions | (4.8) | (15.4)
Payments | 0.0 | 0.0
Lapses in statutes of limitations | (5.8) | (1.4)
Acquired tax positions: |  |
Additions related to reserves acquired from acquisitions | 0.0 | 0.4
Balance as of the end of the fiscal year | $ 101.6 | $ 89.5

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- Definition Unrecognized tax benefits increases. + References No definition available. + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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