Investments: (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 29, 2012	Sep. 29, 2012	Sep. 24, 2011	Dec. 31, 2011
Summary of marketable securities classified as available-for-sale securities
Equity securities, Cost	$ 92,400	$ 92,400		$ 1,015,800
Equity securities, Fair Value	90,400	90,400		1,043,800
Unrealized gains and losses for marketable securities classified as available-for-sale securities in accumulated other comprehensive income
Unrealized gains				32,900
Unrealized losses	(2,000)	(2,000)		(4,900)
Net unrealized gains (losses)	(2,000)	(2,000)		28,000
Realized gains and losses recognized on sales of available-for-sale marketable securities
Realized gains	4,600	46,900
Realized losses		(12,300)	(600)
Net realized gains (losses)	$ 4,600	$ 34,600	$ (600)