Shareholders' Equity: (Details 2) (Stock options, USD $)	6 Months Ended		12 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Dec. 29, 2012
Number of Shares
Outstanding at the beginning of the period (in shares)	613,727
Granted (in shares)	47,500
Exercised (in shares)	(61,851)
Forfeited (in shares)	(6,565)
Outstanding at the end of the period (in shares)	592,811		613,727
Exercisable at the end of the period (in shares)	342,675
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 31.46
Granted (in dollars per share)	$ 59.77
Exercised (in dollars per share)	$ 18.37
Forfeited (in dollars per share)	$ 42.20
Outstanding at the end of the period (in dollars per share)	$ 34.98		$ 31.46
Exercisable at the end of the period (in dollars per share)	$ 24.59
Weighted Average Remaining Contractual Life (years)
Outstanding	6 years 11 months 12 days		7 years 21 days
Exercisable at the end of the period	5 years 8 months 8 days
Intrinsic Value
Outstanding at the beginning of the period	$ 16,010,000
Outstanding at the end of the period	17,719,700		16,010,000
Exercisable at the end of the period	$ 13,802,800
Weighted average assumptions and results used in estimation of fair value of options granted
Risk free interest rate (as a percent)	1.30%	0.88%
Expected life	6 years	6 years
Expected volatility (as a percent)	32.50%	31.40%
Dividend yield (as a percent)	1.90%	2.06%
Option fair value (in dollars per share)	$ 15.84	$ 12.95
2001 Plan
Stock option plans
Number of shares authorized for issuance	750,000
2010 Plan
Stock option plans
Number of shares authorized for issuance	250,000
Nonemployee Directors Plan
Stock option plans
Number of shares authorized for issuance	300,000