GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Components of amortized intangible assets
Gross Carrying Amount	$ 205,079	$ 215,939
Accumulated Amortization	121,486	111,672
Amortization expense for intangible assets	15,935	18,339	$ 18,414
Estimated amortization expense
2016	15,063
2017	13,434
2018	12,694
2019	11,634
2020	9,586
Customer Relationships
Components of amortized intangible assets
Gross Carrying Amount	191,316	201,801
Accumulated Amortization	$ 111,342	$ 101,614
Weighted Average Life	13 years	13 years
Proprietary Software And Database
Components of amortized intangible assets
Gross Carrying Amount	$ 3,616	$ 3,571
Accumulated Amortization	$ 3,056	$ 2,966
Weighted Average Life	8 years	8 years
Patents & Proprietary Technology
Components of amortized intangible assets
Gross Carrying Amount	$ 6,434	$ 6,815
Accumulated Amortization	$ 3,420	$ 3,421
Weighted Average Life	11 years	11 years
Other
Components of amortized intangible assets
Gross Carrying Amount	$ 3,713	$ 3,752
Accumulated Amortization	$ 3,668	$ 3,671
Weighted Average Life	3 years	3 years

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Balance Type:	debit
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References