Income taxes - Reconciliation of Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 28, 2014
Income Tax Disclosure [Abstract]
U.S. statutory tax rate	35.00%	35.00%	35.00%
Increase (decrease) in taxes resulting from:
State taxes (net of federal income tax benefit)	2.80%	3.20%	2.40%
Domestic Manufacturing Deduction	(2.80%)	(2.00%)	(1.60%)
Uncertain tax positions, settlements and lapse of statutes of limitations	(0.30%)	(0.20%)	(0.30%)
Net deferred tax write offs and deferred tax rate adjustments	(1.20%)	(1.60%)	(0.30%)
Non-deductible transactions costs	0.50%	0.50%	0.70%
Loss on sale of subsidiary	0.00%	0.00%	(12.60%)
Non-deductible goodwill	0.00%	0.40%	3.00%
Net excess benefits on share-based payments	(1.00%)	(0.00%)	(0.00%)
Other, net	(0.20%)	0.80%	(0.90%)
Effective tax rate	32.80%	36.10%	25.40%