Investments: (Tables)

6 Months Ended

Jun. 27, 2015

Investments:

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

	June 27, 2015				December 27, 2014
	Cost		Fair Value		Cost		Fair Value
Equity securities	$	238,600	$	215,200	$	526,600	$	466,800

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

	June 27, 2015			December 27, 2014
Unrealized gains	$	—		$	3,300
Unrealized losses	(23,400		)	(63,100		)
Net unrealized losses	$	(23,400	)	$	(59,800	)

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

	Three Months Ended					Six Months Ended
	June 27, 2015		June 28, 2014			June 27, 2015			June 28, 2014
Realized gains	$	—	$	4,600		$	13,400		$	26,800
Realized losses	—		(13,500		)	(36,200		)	(26,300		)
Net realized gains/(losses)	$	—	$	(8,900	)	$	(22,800	)	$	500