Pension Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2018	Jun. 24, 2017	Sep. 30, 2017
Components of net periodic benefit costs included in operating expenses [Abstract]
Contribution to defined pension benefit plan	$ 3,839	$ 7,542
Estimated obligation due to full withdrawal multi employer pension plans	22,773		$ 23,665
Defined Benefit Pension Plan [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Defined benefit plan expected contribution to be paid for fiscal year	4,764
Contribution to defined pension benefit plan	3,839
Post-Retirement Benefits [Member]
Components of net periodic benefit costs included in operating expenses [Abstract]
Defined benefit plan expected contribution to be paid for fiscal year	1,243
Employer contribution for postretirement health care and life insurance	$ 847