Fair Values of Financial Instruments - Summary of Reconciliation of Acquisition Related Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Payments of acquisition related contingent consideration				$ 18,784	$ 18,312
Increase (decrease) in fair value				62,017	1,584
Level 3 [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance - Level 3 liability		$ 412,450	$ 374,537	382,898	381,291
Measurement period adjustment	[1]		(1,279)		813
Payments of acquisition related contingent consideration		(5,948)	(7,049)	(18,784)	(18,312)
Reclassification to current payables		(60)		(940)	(1,540)
Increase (decrease) in fair value		18,749	(2,373)	62,017	1,584
Ending balance - Level 3 liability		$ 425,191	$ 363,836	$ 425,191	$ 363,836

[1] Measurement period adjustments relate to post-closing adjustments made in accordance with the terms and conditions of the applicable asset purchase agreement or asset exchange agreement for distribution territories acquired or exchanged by the Company in April 2017 and October 2017 as part of the System Transformation. All final post-closing adjustments for these transactions were completed during 2018.