Summary Financial Information for National CineMedia (Detail) - NCM - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 28, 2019	Jun. 28, 2018	Jun. 28, 2018	Dec. 27, 2018
Schedule Of Equity Method Investments [Line Items]
Total revenues	$ 76,900	$ 113,700	$ 193,900
Operating income	10,900	40,200	51,200
Net income (loss)	(2,900)	$ 25,000	$ 22,000
Current assets	119,200			$ 172,700
Noncurrent assets	746,000			726,800
Current liabilities	63,400			115,200
Noncurrent liabilities	950,000			924,900
Members deficit	$ (148,200)			$ (140,600)