Pension Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Sep. 28, 2019
Components of net periodic benefit costs included in operating expenses [Abstract]
Contribution to defined pension benefit plan	$ 1,015	$ 925
Estimated obligation due to full withdrawal multi employer pension plans	21,170		$ 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	6,600
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	1,015
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	$ 211