Weighted Average Assumptions Used in the Measurement of Benefit Obligations (Detail) - North America	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Pension Benefits
Weighted Average Discount Rate [Line Items]
Discount rate	4.11%	4.33%	3.91%
Other Benefits, United States
Weighted Average Discount Rate [Line Items]
Discount rate	3.60%	3.70%	3.40%
Other Benefits, Canada
Weighted Average Discount Rate [Line Items]
Discount rate	3.80%	4.00%	4.00%