Investments: (Details) - USD ($)	12 Months Ended
	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Summary of marketable securities classified as available-for-sale securities
Equity securities, Cost	$ 280,600	$ 526,600
Equity securities, Fair Value	227,800	466,800
Unrealized gains and losses for marketable securities classified as available-for-sale securities in accumulated other comprehensive loss
Unrealized gains		3,300	$ 6,800
Unrealized losses	(52,800)	(63,100)	(13,400)
Net unrealized losses	(52,800)	(59,800)	(6,600)
Realized gains and losses recognized on sales of available-for-sale marketable securities
Realized gains	13,400	40,900	25,200
Realized losses	(36,200)	(32,200)
Net realized gains / (losses)	$ (22,800)	$ 8,700	$ 25,200