Net Defined Benefit and Post-Retirement Benefit Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 29, 2013	Mar. 30, 2012	Mar. 29, 2013	Mar. 30, 2012
Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,200	$ 1,100	$ 2,429	$ 2,209
Interest cost	1,295	1,347	2,615	2,691
Plan curtailment			0	(161)
Expected return on plan assets	(1,407)	(1,335)	(2,847)	(2,666)
Amortization of prior service cost	40	40	80	80
Recognized actuarial loss	681	621	1,363	1,242
Net periodic benefit cost	1,809	1,773	3,640	3,395
Post-Retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost	40	55	80	110
Amortization of prior service cost	1	1	2	2
Recognized actuarial loss	15	21	30	42
Net periodic benefit cost	$ 56	$ 77	$ 112	$ 154