Investments: (Tables)

12 Months Ended

Dec. 27, 2014

Investments:

Summary of marketable securities classified as available-for-sale securities

	December 27, 2014				December 28, 2013
	Cost		Fair Value		Cost		Fair Value
Equity securities	$	526,600	$	466,800	$	743,100	$	736,500

Schedule of the Company's unrealized gains and losses for marketable securities classified as available-for-sale securities in accumulated other comprehensive loss

	Year Ended
	December 27, 2014			December 28, 2013			December 29, 2012
Unrealized gains	$	3,300		$	6,800		$	—
Unrealized losses	(63,100		)	(13,400		)	(6,500		)
Net unrealized gains / (losses)	$	(59,800	)	$	(6,600	)	$	(6,500	)

Schedule of the Company's realized gains and losses recognized on sales of available-for-sale marketable securities

	Year Ended
	December 27, 2014			December 28, 2013		December 29, 2012
Realized gains	$	40,900		$	25,200	$	52,500
Realized losses	(32,200		)	—		(31,300		)
Net realized gains	$	8,700		$	25,200	$	21,200