Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]

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- Definition

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

+ References

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-Publisher FASB
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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- Definition

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.

+ References

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- Definition

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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- Definition

The aggregate value of preferred stock dividends and other adjustments necessary to derive net income apportioned to common stockholders.

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- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

+ References

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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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Earnings Per Common Share (Reconciliation Of Numerators And Denominators Of Basic And Diluted Earnings Per Share) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 24, 2017	Mar. 25, 2017	Dec. 24, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 30, 2017	Sep. 24, 2016	Sep. 26, 2015
Class A Common Stock [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Net income allocated, basic									$ 38,393,384	$ 38,380,304	$ 41,356,536
Conversion of Class B to Class A shares									15,480,196	15,809,162	17,996,587
Net income allocated, diluted									$ 53,873,580	$ 54,189,466	$ 59,353,123
Weighted average shares outstanding, basic									14,039,125	13,943,299	13,711,241
Conversion of Class B to Class A shares									6,220,651	6,316,477	6,548,534
Weighted average shares outstanding, diluted									20,259,776	20,259,776	20,259,775
Earnings per share, Basic	$ 0.99	$ 0.58	$ 0.47	$ 0.70	$ 0.72	$ 0.64	$ 0.73	$ 0.66	$ 2.74	$ 2.75	$ 3.02
Earnings per share, Diluted	0.96	0.57	0.45	0.68	0.70	0.63	0.71	0.64	$ 2.66	$ 2.68	$ 2.93
Class B Common Stock [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Net income allocated, basic									$ 15,480,196	$ 15,809,162	$ 17,996,587
Net income allocated, diluted									$ 15,480,196	$ 15,809,162	$ 17,996,587
Weighted average shares outstanding, basic									6,220,651	6,316,477	6,548,534
Weighted average shares outstanding, diluted									6,220,651	6,316,477	6,548,534
Earnings per share, Basic	0.90	0.53	0.42	0.64	0.65	0.59	0.66	0.60	$ 2.49	$ 2.50	$ 2.74
Earnings per share, Diluted	$ 0.90	$ 0.53	$ 0.42	$ 0.64	$ 0.65	$ 0.59	$ 0.66	$ 0.60	$ 2.49	$ 2.50	$ 2.74