Employee Benefit Plans - Additional Information (Details)	12 Months Ended
	Sep. 26, 2015 USD ($) Member	Sep. 27, 2014 USD ($)	Sep. 28, 2013 USD ($) Multiemployerpensionplan
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Minimum funding requirements for defined benefit pension plan	$ 0	$ 0	$ 0
Defined benefit plan expected future benefit payments	700,000
Pension settlement payments to either terminated or retired individuals	5,777,000
Settlement threshold amount	5,128,000
Pension settlement charge	$ 2,000,000	0	0
Health care cost trend	4.50%
Health care cost trend rate (in hundredths)	7.10%
Percentage of sensitivity increase or decrease of assumed health care cost trend rates (in hundredths)	1.00%
Estimated obligation due to withdrawal multi employer pension plans	$ 18,041,000	6,880,000	$ 7,000,000
Number of voluntary partial withdrawal from multi employer pension plans | Multiemployerpensionplan			1
Number of full withdrawal from multi employer pension plans | Multiemployerpensionplan			4
Increase in estimated obligation due to withdrawal multi employer pension plans	11,300,000
Contributions	1,073,000	1,168,000	$ 1,162,000
Health and Welfare Benefits and Defined Annuity Plans [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Contributions	$ 1,817,000	1,897,000	$ 2,040,000
Red [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Multiemployer plans, funded status	Less than 65 percent
Yellow [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Multiemployer plans, funded status	Between 65 and less than 80 percent
Green [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Multiemployer plans, funded status	At least 80 percent
Pension Benefits [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Expenses (credits) in accumulated other comprehensive loss expected to be recognized as components of net period benefit costs in succeeding fiscal year	$ 5,218,000
Number of members on the Benefits Committee | Member	6
Pension settlement payments to either terminated or retired individuals	$ 5,777,000	$ 5,401,000
Pension settlement charge	$ (2,000,000)
Percentage threshold of the greater of projected benefit obligation and market-related value plan assets as unrecognized actuarial gains and losses (in hundredths)	10.00%
Pension Benefits [Member] | Fixed income securities [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Allocation percentage of plan assets, range minimum (in hundredths)	80.00%
Allocation percentage of plan assets, range maximum (in hundredths)	90.00%
Pension Benefits [Member] | Equity securities [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Allocation percentage of plan assets, range minimum (in hundredths)	10.00%
Allocation percentage of plan assets, range maximum (in hundredths)	20.00%
Retiree Health and Life Benefits [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Expenses (credits) in accumulated other comprehensive loss expected to be recognized as components of net period benefit costs in succeeding fiscal year	$ (698,000)
Health care cost trend	7.10%	7.12%
Health care cost trend rate (in hundredths)	7.12%	7.33%	7.53%
Retirement Savings and Investment Plan 401(K) [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Contributions to the 401(k) Plan	$ 1,844,000	$ 1,848,000	$ 1,915,000