Net Income per Share - Computation of Earnings Per Share, Basic (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 27, 2021	Mar. 28, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income		$ 65,565	$ 18,234
Allocation of net income for basic:
Allocation of net income for basic common stock		$ 65,565	$ 18,234
Weighted average number of shares for basic:
Weighted-average number of common shares — basic		12,271	12,157
Net income per share for basic:
Net income per common share - basic		$ 5.34	$ 1.50
Common Class A
Allocation of net income for basic:
Allocation of net income for basic common stock		$ 53,628	$ 14,136
Weighted average number of shares for basic:
Weighted-average number of common shares — basic		10,037	9,425
Net income per share for basic:
Net income per common share - basic		$ 5.34	$ 1.50
Common Class B
Allocation of net income for basic:
Allocation of net income for basic common stock		$ 11,638	$ 3,967
Weighted average number of shares for basic:
Weighted-average number of common shares — basic	[1]	2,178	2,645
Net income per share for basic:
Net income per common share - basic		$ 5.34	$ 1.50
Unvested participating shares
Allocation of net income for basic:
Allocation of net income for basic unvested participating shares		$ 299	$ 131
Weighted average number of shares for basic:
Weighted-average number of common shares — basic		56	87

[1] Change in Class B Common Stock resulted from the conversion of 215,000 shares to Class A Common Stock on May 6, 2020 and 130,000 shares to Class A Common Stock on November 3, 2020 with the ending number of shares reflecting the weighted average for the period.