Shareholders' Equity - Additional Information (Detail)	12 Months Ended
	Sep. 24, 2016 USD ($) vote $ / shares shares	Sep. 26, 2015 $ / shares shares	Sep. 24, 2011 USD ($)
Class of Stock [Line Items]
Preferred stock authorized (in shares)	1,000,000	1,000,000
Preferred stock, par value (in usd per share) | $ / shares	$ 0.01	$ 0.01
Preferred stock, shares outstanding	0	0
Common Stock [Member]
Class of Stock [Line Items]
Common stock authorized (in shares)	80,000,000
Common stock, par value (in usd per share) | $ / shares	$ 0.01
Common stock, shares outstanding	11,998,472
Authorized amount to repurchase stock | $			$ 100,000,000
Aggregate stock repurchased shares	7,900,000
Aggregate stock repurchased value | $	$ 65,000,000
Class A Common Stock [Member]
Class of Stock [Line Items]
Common stock authorized (in shares)	100,000,000
Common stock, par value (in usd per share) | $ / shares	$ 0.01
Common stock, shares outstanding	37,418,572
Class B Stock [Member]
Class of Stock [Line Items]
Common stock authorized (in shares)	3,000,000	3,000,000
Common stock, par value (in usd per share) | $ / shares	$ 0.01	$ 0.01
Common stock, shares outstanding	1,652,262	1,652,262
Percentage of vote cast for shares (percent)	49.00%
Convertible shares conversion ratio	1
Minimum [Member] | Class B Stock [Member]
Class of Stock [Line Items]
Number of voting powers | vote	1
Maximum [Member] | Class B Stock [Member]
Class of Stock [Line Items]
Number of voting powers | vote	10