Computations of Basic Earnings Per Share and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 30, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 30, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic Earnings per Share:
Net Income	$ 6,194	$ 6,292	$ 5,967	$ 5,602	$ 5,573	$ 5,167	$ 4,864	$ 4,645	$ 24,055	$ 20,249	$ 13,405
Weighted Average Shares Outstanding									12,622,049	12,581,646	11,098,836
Basic Earnings per Share	$ 0.49	$ 0.50	$ 0.47	$ 0.44	$ 0.44	$ 0.41	$ 0.39	$ 0.37	$ 1.91	$ 1.61	$ 1.21
Diluted Earnings per Share:
Net Income	$ 6,194	$ 6,292	$ 5,967	$ 5,602	$ 5,573	$ 5,167	$ 4,864	$ 4,645	$ 24,055	$ 20,249	$ 13,405
Weighted Average Shares Outstanding									12,622,049	12,581,646	11,098,836
Stock Options, Net									15,694	6,102	6,051
Diluted Weighted Average Shares Outstanding									12,637,743	12,587,748	11,104,887
Diluted Earnings per Share	$ 0.49	$ 0.50	$ 0.47	$ 0.44	$ 0.44	$ 0.41	$ 0.39	$ 0.37	$ 1.90	$ 1.61	$ 1.21