Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended	6 Months Ended
Mar. 30, 2013	Mar. 24, 2012	Mar. 30, 2013	Mar. 24, 2012
Class A Common Stock
Numerator: Allocated net income
Net income allocated, basic	$ 4,513,615	$ 3,620,798	$ 10,962,905	$ 9,492,303
Conversion of Class B to Class A shares	3,576,541	2,891,277	8,694,898	7,616,988
Net income allocated, diluted	8,090,156	6,512,075	19,657,803	17,109,291
Denominator: Weighted average shares outstanding
Weighted average shares outstanding, basic	12,961,853	12,926,684	12,958,169	12,932,887
Conversion of Class B to Class A shares	11,297,923	11,359,090	11,301,607	11,411,906
Weighted average shares outstanding, diluted	24,259,776	24,285,774	24,259,776	24,344,793
Earnings per share
Basic	$ 0.35	$ 0.28	$ 0.85	$ 0.73
Diluted	$ 0.33	$ 0.27	$ 0.81	$ 0.70
Class B Common Stock
Numerator: Allocated net income
Net income allocated, basic	3,576,541	2,891,277	8,694,898	7,616,988
Conversion of Class B to Class A shares
Net income allocated, diluted	$ 3,576,541	$ 2,891,277	$ 8,694,898	$ 7,616,988
Denominator: Weighted average shares outstanding
Weighted average shares outstanding, basic	11,297,923	11,359,090	11,301,607	11,411,906
Conversion of Class B to Class A shares
Weighted average shares outstanding, diluted	11,297,923	11,359,090	11,301,607	11,411,906
Earnings per share
Basic	$ 0.32	$ 0.26	$ 0.77	$ 0.67
Diluted	$ 0.32	$ 0.26	$ 0.77	$ 0.67

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent, and includes adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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