Fair Values of Financial Instruments - Summary of Reconciliation of Acquisition Related Contingent Consideration (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Apr. 01, 2018
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Payment of acquisition related contingent consideration		$ 6,237	$ 5,882
(Favorable)/unfavorable fair value adjustment		14,046	(5,186)
Level 3 [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance - Level 3 liability		382,898	381,291
Measurement period adjustment	[1]		(1,059)
Payment of acquisition related contingent consideration		(6,237)	(5,882)
Reclassification to current payables		2,300	(360)
(Favorable)/unfavorable fair value adjustment		14,046	(5,186)
Ending balance - Level 3 liability		$ 393,007	$ 368,804

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