Retirement Plans (Reconciliation of Fair Value of Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 27, 2014	Dec. 28, 2013
Reconciliation of Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	$ 267,635	$ 260,917
Pensions [Member]
Reconciliation of Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	260,917	231,897
Actual return on plan assets	18,466	32,085
Employer contributions	11,925	13,567
Benefits paid	(23,673)	(16,632)
Fair value of plan assets at end of year	267,635	260,917
Supplemental Employee Retirement Plans [Member]
Reconciliation of Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,995	2,094
Benefits paid	(1,995)	(2,094)
Fair value of plan assets at end of year	0	0
Other Postretirement Benefit Plans [Member]
Reconciliation of Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	122	136
Benefits paid	(122)	(136)
Fair value of plan assets at end of year	$ 0	$ 0

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost)

-URI http://asc.fasb.org/extlink&oid=6504192

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost)

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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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Benefits

-URI http://asc.fasb.org/extlink&oid=6506267

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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The increase in the fair value of plan assets from contributions made by the employer.

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+ References

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

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