Employee Benefit Plans - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Pension Benefits [Member]
Reconciliation of benefit obligations:
Benefit obligation at beginning of year	$ 115,471	$ 111,701
Interest cost	2,726	3,943	$ 3,778
Actuarial loss (gain)	7,005	10,429
Lump sum benefits paid	(3,623)	(3,869)	(3,373)
Ordinary benefits paid	(6,347)	(6,733)
Benefit obligation at end of year	115,232	115,471	111,701
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of year	80,913	78,032
Actual gain (loss) return on plan assets	5,223	8,133
Employer contributions	3,835	5,350	4,764
Lump sum benefits paid	(3,623)	(3,869)
Ordinary benefits paid	(6,347)	(6,733)
Fair value of plan assets at end of year	80,001	80,913	78,032
Funded status:
Funded status at end of year	(35,231)	(34,558)
Amounts recognized in consolidated balance sheets consist of:
Net amount recognized at end of year	(35,231)	(34,558)
Less: current portion	0	0
Noncurrent benefit liability	(35,231)	(34,558)
Amounts not yet recognized in net periodic benefit cost and included in accumulated other comprehensive income (loss):
Actuarial net (loss) gain	(32,286)	(33,733)
Prior service credits	0	0
Net amount recognized in accumulated other comprehensive (loss) income	(32,286)	(33,733)
Retiree Health and Life Benefits [Member]
Reconciliation of benefit obligations:
Benefit obligation at beginning of year	6,929	7,895
Interest cost	151	275	277
Actuarial loss (gain)	(246)	(296)
Lump sum benefits paid	0	0
Ordinary benefits paid	(835)	(945)
Benefit obligation at end of year	5,999	6,929	7,895
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of year	0	0
Actual gain (loss) return on plan assets	0	0
Employer contributions	835	945
Lump sum benefits paid	0	0
Ordinary benefits paid	(835)	(945)
Fair value of plan assets at end of year	0	0	$ 0
Funded status:
Funded status at end of year	(5,999)	(6,929)
Amounts recognized in consolidated balance sheets consist of:
Net amount recognized at end of year	(5,999)	(6,929)
Less: current portion	843	970
Noncurrent benefit liability	(5,156)	(5,959)
Amounts not yet recognized in net periodic benefit cost and included in accumulated other comprehensive income (loss):
Actuarial net (loss) gain	4,757	5,296
Prior service credits	1,753	2,251
Net amount recognized in accumulated other comprehensive (loss) income	$ 6,510	$ 7,547