Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 24, 2016	Dec. 26, 2015
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1,041	$ 1,260
Expected return on plan assets	(537)	(854)
Amortization of net loss (gain)	1,300	1,134
Net periodic benefit cost	1,804	1,540
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	96	130
Amortization of prior service credits	0	(100)
Amortization of net loss (gain)	(97)	(75)
Net periodic benefit cost	$ (1)	$ (45)