GOODWILL AND INTANGIBLE ASSETS - Amortized Intangible Assets - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014	Dec. 27, 2014
Components of amortized intangible assets
Gross Carrying Amount	$ 222,225		$ 222,225		$ 228,027
Accumulated Amortization	114,427		114,427		103,050
Amortization expense for intangible assets	4,507	$ 4,702	14,157	$ 13,439
Estimated amortization expense
2015	18,154		18,154
2016	15,944		15,944
2017	15,898		15,898
2018	14,261		14,261
2019	13,434		13,434
Customer Relationships
Components of amortized intangible assets
Gross Carrying Amount	202,199		202,199		207,509
Accumulated Amortization	98,523		$ 98,523		$ 88,538
Weighted Average Life			13 years		13 years
Proprietary Software & Database
Components of amortized intangible assets
Gross Carrying Amount	3,534		$ 3,534		$ 3,769
Accumulated Amortization	2,929		$ 2,929		$ 2,977
Weighted Average Life			8 years		8 years
Patents & Proprietary Technology
Components of amortized intangible assets
Gross Carrying Amount	12,659		$ 12,659		$ 12,394
Accumulated Amortization	9,211		$ 9,211		$ 8,537
Weighted Average Life			8 years		8 years
Other
Components of amortized intangible assets
Gross Carrying Amount	3,833		$ 3,833		$ 4,355
Accumulated Amortization	$ 3,764		$ 3,764		$ 2,998
Weighted Average Life			3 years		3 years