Schedule of Assumptions Used to Determine Net Periodic Benefit Cost (Detail)	12 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 28, 2012
Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.11%	2.94%	3.38%
Rate of compensation increase	2.51%	2.37%	2.48%
Expected long-term return on assets	4.21%	3.82%	4.02%
Post-Retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.80%	3.00%	3.90%