Shareholders' Equity: (Details 2) (USD $)	6 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014 Employee and Directors Stock Options [Member]	Jun. 28, 2014 Employee and Directors Stock Options [Member]	Dec. 28, 2013 Employee and Directors Stock Options [Member]	Jun. 28, 2014 Stock Option Plan 2001 [Member] Employee and Directors Stock Options [Member]	Jun. 28, 2014 Stock Option Plan 2010 [Member] Employee and Directors Stock Options [Member]	Apr. 30, 2014 Stock Option Plan 2010 [Member] Employee and Directors Stock Options [Member]	Jun. 28, 2014 Stock Option Plan for Nonemployee Directors [Member] Employee and Directors Stock Options [Member]	Apr. 30, 2014 Stock Option Plan for Nonemployee Directors [Member] Employee and Directors Stock Options [Member]
Stock option plans
Number of shares authorized for issuance						750,000	500,000	250,000	350,000	300,000
Number of Shares
Outstanding at the beginning of the period (in shares)				526,712
Granted (in shares)				48,500
Exercised (in shares)				(20,012)
Forfeited (in shares)				(5,000)
Outstanding at the end of the period (in shares)			550,200	550,200	526,712
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)				$ 42.87
Granted (in dollars per share)				$ 66.29
Exercised (in dollars per share)				$ 19.59
Forfeited (in dollars per share)				$ 56.85
Outstanding at the end of the period (in dollars per share)			$ 45.65	$ 45.65	$ 42.87
Exercisable at the end of the period (in dollars per share)			$ 33.17	$ 33.17
Exercisable at the end of the period (in shares)			305,748	305,748
Weighted Average Remaining Contractual Life (years)
Outstanding				7 years 1 month 24 days	7 years 3 months 29 days
Exercisable at the end of the period			5 years 11 months 16 days
Intrinsic Value
Outstanding at the beginning of the period				$ 26,446,700
Outstanding at the end of the period			14,842,200	14,842,200	26,446,700
Exercisable at the end of the period			$ 11,417,400	$ 11,417,400
Weighted average assumptions and results used in estimation of fair value of options granted
Risk free interest rate (as a percent)	1.80%	1.30%
Expected life (years)	6 years	6 years
Expected volatility (as a percent)	34.10%	32.50%
Dividend yield (as a percent)	1.80%	1.90%
Option fair value (in dollars per share)	$ 19.23	$ 15.84