Computation of Earnings Per Share, Basic (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, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income		$ 16,115	$ 38,624	$ 29,932	$ 13,743	$ 19,074	$ 37,926	$ 25,428	$ 8,315	$ 98,414	$ 90,743	$ 70,392
Allocation of net income for basic:
Allocation of net income for basic common stock										98,414	90,743	70,392
Allocation of net income for basic unvested participating shares										$ 462	$ 509	$ 510
Weighted average number of shares for basic:
Weighted average number of shares for basic unvested participating shares										62	73	93
Shares used in net income per common share - basic										13,185	13,041	12,859
Net income per share for basic:
Net Income Per Common Stock		$ 1.25	$ 2.93	$ 2.24	$ 1.04	$ 1.46	$ 2.91	$ 1.95	$ 0.64	$ 7.46	$ 6.96	$ 5.47
Common Class A
Allocation of net income for basic:
Allocation of net income for basic common stock										$ 71,798	$ 64,027	$ 47,847
Weighted average number of shares for basic:
Weighted average number of shares for basic common stock										9,619	9,202	8,741
Net income per share for basic:
Net Income Per Common Stock										$ 7.46	$ 6.96	$ 5.47
Common Class B
Allocation of net income for basic:
Allocation of net income for basic common stock										$ 26,154	$ 26,207	$ 22,035
Weighted average number of shares for basic:
Weighted average number of shares for basic common stock	[1]									3,504	3,766	4,025
Net income per share for basic:
Net Income Per Common Stock										$ 7.46	$ 6.96	$ 5.47

[1] Change in Class B Common Stock resulted from the conversion of 150,000 shares to Class A Common Stock on May 6, 2015 and 100,000 shares to Class A Common Stock on October 26, 2015, with the 52-week number of shares reflecting the weighted average for the period.