Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Share Amounts (Detail) - shares shares in Thousands	12 Months Ended
Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Earnings Per Share [Line Items]
Basic weighted average common shares outstanding (in shares)	262,727	269,413	275,105
Weighted average common stock equivalents from assumed exercise of stock options and restricted stock units (in shares)	1,886	0	0
Diluted weighted average common shares outstanding (in shares)	264,613	269,413	275,105
Outstanding Stock Options and stock units [Member]
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	1,158	4,098	5,073
Convertible Notes
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	0	0	703

Earnings Per Share [Line Items]

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Weighted average common stock equivalents from assumed exercise of stock options and restricted stock units

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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