Weighted Average Assumptions Used in the Measurement of Net Periodic Benefit Cost (Detail) (North America)	12 Months Ended
	Dec. 27, 2014	Dec. 28, 2013
Pension Benefits
Schedule of Net Periodic Benefit Costs Weighted Average Assumptions [Line Items]
Discount rate	4.84%	4.76%
Expected long-term rate of return on plan assets	6.50%	6.60%
Other Benefits, United States
Schedule of Net Periodic Benefit Costs Weighted Average Assumptions [Line Items]
Discount rate	4.00%	3.80%
Other Benefits, Canada
Schedule of Net Periodic Benefit Costs Weighted Average Assumptions [Line Items]
Discount rate	4.80%	4.60%