Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Share Amounts (Detail) - shares shares in Thousands	12 Months Ended
Sep. 30, 2017	Sep. 24, 2016	Sep. 26, 2015
Earnings Per Share [Line Items]
Basic weighted average common shares outstanding (in shares)	279,811	280,213	280,566
Weighted Average Common Stock Equivalents From Assumed Exercise Of Stock Options And Restricted Stock Units	2,885	2,631	2,898
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	2,957	3,312	6,073
Diluted weighted average common shares outstanding (in shares)	285,653	286,156	289,537
Outstanding Stock Options [Member]
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	1,677	1,029	1,502
Restricted Stock Units [Member]
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	12	62	49

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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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6510752

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-Publisher FASB
-Name Accounting Standards Codification
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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

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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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