Computation of Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 27, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
As reported - basic									$ 98,414	$ 90,743	$ 70,392
Net income per common share - diluted									13,520	13,484	13,504
As reported - basic	$ 1.25	$ 2.93	$ 2.24	$ 1.04	$ 1.46	$ 2.91	$ 1.95	$ 0.64	$ 7.46	$ 6.96	$ 5.47
Net income per common share - diluted	$ 1.21	$ 2.85	$ 2.18	$ 1.00	$ 1.40	$ 2.79	$ 1.88	$ 0.62	$ 7.25	$ 6.69	$ 5.18
Common Class A
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
As reported - basic									$ 71,798	$ 64,027	$ 47,847
Class B Common Stock									26,154	26,207	22,035
Net effect of unvested participating shares									14	19	28
Net income per common share - diluted									$ 97,966	$ 90,253	$ 69,910
As reported - basic									9,619	9,202	8,741
Add: effect of dilutive potential common share-based awards									397	516	738
Class B Common Stock									3,504	3,766	4,025
Net income per common share - diluted									13,520	13,484	13,504
As reported - basic									$ 7.46	$ 6.96	$ 5.47
Net income per common share - diluted									$ 7.25	$ 6.69	$ 5.18