Pension Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2021	Mar. 28, 2020	Mar. 27, 2021	Mar. 28, 2020	Sep. 26, 2020
Components of net periodic benefit costs included in operating expenses [Abstract]
Contribution to defined pension benefit plan			$ 3,690	$ 2,030
Estimated obligation due to full withdrawal multi employer pension plans	$ 19,876		19,876		$ 20,396
Pension settlement charge			570	0
Defined Benefit Pension Plan [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Defined benefit plan expected future benefit payments	6,250		6,250
Settlement threshold amount			2,135
Pension settlement charge	570	$ 0	570	$ 0
Defined Benefit Pension Plan [Member] | Other, Net [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Contribution to defined pension benefit plan			3,690
Post-Retirement Benefits [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Defined benefit plan expected future benefit payments	$ 843		843
Post-Retirement Benefits [Member] | Other, Net [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Employer contribution for postretirement health care and life insurance			$ 374