Balance Sheet Components - Components of Other Long-Term Liabilities (Detail) - USD ($) $ in Millions	Sep. 28, 2018	Sep. 29, 2017
Balance Sheet Related Disclosures [Abstract]
Long-term income taxes payable	$ 189.1	$ 48.6
Long-term deferred revenues	38.6	7.2
Deferred income taxes	31.4	17.1
Other	65.2	54.5
Total other long-term liabilities	$ 324.3	$ 127.4

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