Business Acquisitions - Additional Information (Detail) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($) business	Dec. 30, 2017 USD ($) broadline_distributor	Dec. 30, 2017 specialty_distributor
Business Combinations [Abstract]
Business acquisitions during the period	0	3	2
Cash consideration for acquisition		$ 182.0
Estimated fair value of earnout liabilities	$ 0.5
Post-closing earnout period	2 years
Aggregate contingent consideration outstanding for acquisition	$ 5.0