Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2016	Dec. 26, 2015
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 50,000	$ 52,000
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Ratio for converting shares of Class B common stock into shares of Class A common stock, numerator (in Class A shares)	1	1
Ratio for converting shares of Class B common stock into shares of Class A common stock, denominator (in Class B shares)	1	1
Treasury stock, shares	1,740,152	1,711,011
Common Class A
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, authorized shares	25,000,000	25,000,000
Common stock, issued shares	16,939,634	16,626,981
Common Class B
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, authorized shares	5,000,000	5,000,000
Common stock, issued shares	1,688,111	1,742,482