GOODWILL AND INTANGIBLE ASSETS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Mar. 26, 2011	Dec. 31, 2011	Mar. 31, 2012 Customer Relationships Y	Dec. 31, 2011 Customer Relationships Y	Mar. 31, 2012 Proprietary Software and Database Y	Dec. 31, 2011 Proprietary Software and Database Y	Mar. 31, 2012 Patents and Proprietary Technology Y	Dec. 31, 2011 Patents and Proprietary Technology Y	Mar. 31, 2012 Non-compete Agreements Y	Dec. 31, 2011 Non-compete Agreements Y
Components of amortized intangible assets
Gross Carrying Amount	$ 172,918		$ 170,046	$ 158,255	$ 155,629	$ 3,130	$ 3,116	$ 9,707	$ 9,489	$ 1,826	$ 1,812
Accumulated Amortization	62,107		57,988	53,668	50,107	2,739	2,711	4,323	3,863	1,377	1,307
Weighted Average Life (in years)				13	13	6	6	8	8	6	6
Amortization expense for intangible assets	3,545	3,532
Estimated amortization expense
2012	14,243
2013	13,383
2014	12,957
2015	12,060
2016	$ 11,479