Pension Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Sep. 28, 2019
Components of net periodic benefit costs included in operating expenses [Abstract]
Contribution to defined pension benefit plan	$ 2,030	$ 3,320
Estimated obligation due to full withdrawal multi employer pension plans	20,910		$ 21,441
Defined Benefit Pension Plan [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Defined benefit plan expected future benefit payments	3,800
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	2,030
Post-Retirement Benefits [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Defined benefit plan expected future benefit payments	970
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	$ 444