Pension Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 30, 2017	Dec. 24, 2016	Sep. 30, 2017
Components of net periodic benefit costs included in operating expenses [Abstract]
Contribution to defined pension benefit plan	$ 0	$ 1,396
Estimated obligation due to full withdrawal multi employer pension plans	23,389		$ 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	10,290
Contribution to defined pension benefit plan	0
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	$ 258