Employee Benefit Plans - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 26, 2015
Pension Benefits [Member]
Reconciliation of benefit obligations:
Benefit obligation at beginning of year	$ 150,363,000	$ 146,907,000
Interest cost	4,164,000	5,041,000	$ 5,128,000
Actuarial (gain) loss	(4,018,000)	11,547,000
Lump sum benefits paid	(20,799,000)	(5,816,000)	(5,777,000)
Ordinary benefits paid	(7,063,000)	(7,316,000)
Plan amendment	0	0
Benefit obligation at end of year	122,647,000	150,363,000	146,907,000
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of year	101,077,000	104,303,000
Actual return on plan assets	911,000	9,191,000
Employer contributions	11,523,000	715,000	0
Lump sum benefits paid	(20,799,000)	(5,816,000)
Ordinary benefits paid	(7,063,000)	(7,316,000)
Fair value of plan assets at end of year	85,649,000	101,077,000	104,303,000
Funded status:
Funded status at end of year	(36,998,000)	(49,286,000)
Amounts recognized in consolidated balance sheets consist of:
Net amount recognized at end of year	(36,998,000)	(49,286,000)
Less: current portion	0	0
Noncurrent benefit liability	(36,998,000)	(49,286,000)
Amounts not yet recognized in net periodic benefit cost and included in accumulated other comprehensive income (loss):
Actuarial net (loss) gain	(37,311,000)	(51,391,000)
Prior service credits	0	0
Net amount recognized in accumulated other comprehensive (loss) income	(37,311,000)	(51,391,000)
Retiree Health and Life Benefits [Member]
Reconciliation of benefit obligations:
Benefit obligation at beginning of year	13,778,000	15,294,000
Interest cost	385,000	520,000	575,000
Actuarial (gain) loss	123,000	(1,198,000)
Lump sum benefits paid	0	0
Ordinary benefits paid	(1,187,000)	(838,000)
Plan amendment	(3,246,000)	0
Benefit obligation at end of year	9,853,000	13,778,000	15,294,000
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,187,000	838,000
Lump sum benefits paid	0	0
Ordinary benefits paid	(1,187,000)	(838,000)
Fair value of plan assets at end of year	0	0	0
Funded status:
Funded status at end of year		(13,778,000)	$ (9,853,000)
Amounts recognized in consolidated balance sheets consist of:
Net amount recognized at end of year	(9,853,000)	(13,778,000)
Less: current portion	1,243,000	922,000
Noncurrent benefit liability	(8,610,000)	(12,856,000)
Amounts not yet recognized in net periodic benefit cost and included in accumulated other comprehensive income (loss):
Actuarial net (loss) gain	5,253,000	5,764,000
Prior service credits	3,246,000	0
Net amount recognized in accumulated other comprehensive (loss) income	$ 8,499,000	$ 5,764,000