Retirement Plans - Components of Net Pension Expense and Periodic Benefit Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 25, 2012	Mar. 31, 2013	Mar. 25, 2012
Disclosure Retirement Plans Components Of Net Pension Expense And Periodic Benefit Costs [Abstract]
Expected return on assets	$ (1,176)	$ (1,023)	$ (2,352)	$ (2,047)
Service cost	1,229	976	2,458	1,951
Interest cost	1,115	1,091	2,229	2,183
Amortization of prior service cost	1	1	2	2
Amortization of recognized losses	725	529	1,451	1,057
Net pension expense	$ 1,894	$ 1,574	$ 3,788	$ 3,146