Retirement Plans (Funded Status and Net Periodic Cost) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 27, 2014	Dec. 28, 2013	Dec. 29, 2012
Reconciliation of Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 336,975
Service cost	2us-gaap_DefinedBenefitPlanServiceCost	0us-gaap_DefinedBenefitPlanServiceCost	1,932us-gaap_DefinedBenefitPlanServiceCost
Interest cost	14,870us-gaap_DefinedBenefitPlanInterestCost	13,716us-gaap_DefinedBenefitPlanInterestCost	14,546us-gaap_DefinedBenefitPlanInterestCost
Actuarial loss (gain)	3,220	7,779	6,424
Benefit obligation at end of year	383,834	336,975
Pensions [Member]
Reconciliation of Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	319,151	352,009
Service cost	0	0
Interest cost	14,027	12,932
Actuarial loss (gain)	55,821	(29,158)
Benefits paid	(23,673)	(16,632)
Prior service cost due to acquisition	0	0
Benefit obligation at end of year	365,326	319,151
Supplemental Employee Retirement Plans [Member]
Reconciliation of Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	17,824	19,603
Service cost	0	0
Interest cost	754	696
Actuarial loss (gain)	1,925	(381)
Benefits paid	(1,995)	(2,094)
Prior service cost due to acquisition	0	0
Benefit obligation at end of year	18,508	17,824
Other Postretirement Benefit Plans [Member]
Reconciliation of Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	2,075	2,479
Service cost	2	0
Interest cost	88	88
Actuarial loss (gain)	(254)	(418)
Benefits paid	(122)	(136)
Prior service cost due to acquisition	0	62
Benefit obligation at end of year	$ 1,789	$ 2,075

Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Gain or Loss

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- Definition

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

+ References

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-Glossary Projected Benefit Obligation

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Glossary Accumulated Postretirement Benefit Obligation

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Postretirement Benefits

-URI http://asc.fasb.org/extlink&oid=6521376

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The amount of increase in the benefit obligation attributed to business combinations.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

+ References

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-Glossary Service Cost (Component of Net Periodic Pension Cost)

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