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Earnings Per Share Data - Additional Information (Detail)		3 Months Ended
	Jul. 11, 2016	Dec. 31, 2016 shares	Dec. 31, 2015 shares
Earnings Per Share [Line Items]
Exercisable stock options, included in the diluted earnings per share calculation		482,000	488,000
Effect of dilutive stock options		209,000	118,000
Anti-dilutive exercisable stock options, not included in the diluted earnings per share calculation		0	0
Common and Class B Stock [Member]
Earnings Per Share [Line Items]
Stock split ratio	1.5
Stock dividend percentage	50.00%
Stock split ratio description		On July 11, 2016, the Company's Board of Directors approved a three-for-two split of the Company's common and Class B stock to be effected in the form of a 50% stock dividend. As a result, shareholders received one additional share of common or Class B stock for every two shares they held of the respective class of stock as of the record date.

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Common stock dividend rate percentage.

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Earnings Per Share [Line Items]

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6508534

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Number of options vested.

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Description of the stock split arrangement. Also provide the retroactive effect given by a stock split that occurs after the balance date but before the release of financial statements.

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Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

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