Commitments and Contingencies: (Details) - USD ($)	12 Months Ended
	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Employee Benefit Plan
Service period for vesting of employer contribution	5 years
Company contributions	$ 324,600	$ 297,400	$ 281,900
Operating Leases
Rent expense under operating leases	1,063,900	1,026,800	$ 883,800
Minimum rental commitments
2016	691,200
2017	705,000
2018	718,800
2019	451,100
Total	2,566,100
Total deferred rent	800,000	1,000,000
Deferred rent included in other liabilities	$ 600,000	$ 800,000