Defined Benefit Plan Ultimate Health Care Cost Trend Rate Twenty Forty.

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Increase in multiemployer plans withdrawal obligation.

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The number of members serving on the Benefits Committee.

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Refers to number of voluntary partial withdrawal from multi employer pension plans.

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Sensitivity expressed as a percentage to determine a material impact to financial statement or related disclosures.

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The percentage threshold for unrecognized actuarial gains or losses in excess the greater of the projected benefit obligation and fair value of plan assets.

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Settlement threshold amount includes service and interest cost.

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Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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Amount of contributions received and expected to be received by defined benefit plan from employer in current fiscal year.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

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Amount of (increase) decrease to benefit obligation of defined benefit plan from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Includes, but is not limited to, lump-sum cash payment to participant in exchange for right to receive specified benefits, purchase of nonparticipating annuity contract and change from remeasurement.

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- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

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Percentage employer matches of the employee's percentage contribution matched.

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Amount of cost for employer contribution to multiemployer pension plan determined to be individually significant.

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Indicates whether multiemployer pension plan determined to be individually significant is less than 65 percent funded, between 65 and less than 80 percent funded, or at least 80 percent funded. Acceptable values are "Less than 65 percent", "Between 65 and less than 80 percent", "At least 80 percent", and "NA".

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Amount of the obligation recognized by withdrawing from a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

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No definition available.

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Employee Benefit Plans - Additional Information (Details)	12 Months Ended
	Sep. 26, 2020 USD ($) Member	Sep. 28, 2019 USD ($)	Sep. 29, 2018 USD ($)	Sep. 24, 2016 USD ($)	Sep. 26, 2015 USD ($)	Sep. 28, 2013 USD ($) Multiemployerpensionplan
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Settlement charge	$ 1,051,000	$ 0	$ 0
Estimated obligation due to withdrawal multi employer pension plans	$ 20,396,000	21,441,000				$ 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				$ 6,600,000	$ 11,300,000
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
Health and Welfare Benefits and Defined Annuity Plans [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Contributions	$ 1,151,000	1,220,000	1,099,000
United States [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
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]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Contributions for defined benefit pension plan	$ 3,835,000	5,350,000	4,764,000
Expenses (credits) in accumulated other comprehensive loss expected to be recognized as components of net period benefit costs in succeeding fiscal year	$ 3,592,000
Number of members on the Benefits Committee \| Member	6
Defined benefit plan expected future benefit payments	$ 6,250,000
Pension settlement payments to either terminated or retired individuals	3,623,000	3,869,000	3,373,000
Settlement threshold amount	2,725,000	3,943,000	3,778,000
Settlement charge	$ 1,051,000	$ 0	0
Health care cost trend rate (in hundredths)	0.00%	0.00%
Retiree Health and Life Benefits [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Contributions for defined benefit pension plan	$ 835,000	$ 945,000
Expenses (credits) in accumulated other comprehensive loss expected to be recognized as components of net period benefit costs in succeeding fiscal year	(1,221,000)
Pension settlement payments to either terminated or retired individuals	0	0
Settlement charge	$ 0	$ 0	0
Health care cost trend (in hundredths), twenty forty	4.50%
Health care cost trend rate (in hundredths)	5.72%	6.01%
Percentage of sensitivity increase or decrease of assumed health care cost trend rates (in hundredths)	1.00%
Maximum [Member] \| Pension Benefits [Member] \| Fixed income securities [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Allocation percentage of plan assets (in hundredths)	90.00%
Maximum [Member] \| Pension Benefits [Member] \| Equity securities [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Allocation percentage of plan assets (in hundredths)	20.00%
Minimum [Member] \| Pension Benefits [Member] \| Fixed income securities [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Allocation percentage of plan assets (in hundredths)	80.00%
Minimum [Member] \| Pension Benefits [Member] \| Equity securities [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Allocation percentage of plan assets (in hundredths)	10.00%
Retiree Health and Life Benefits [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Employer contribution match amount	$ 0.50
Contribution costs to the 401(k) Plan	$ 3,934,000	$ 3,782,000	$ 3,575,000
Retiree Health and Life Benefits [Member] \| Maximum [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Eligible compensation match percentage	6.00%