Goodwill and Other Intangible Assets (Schedule of Goodwill and Other Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 28, 2013	Dec. 29, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Gross Carrying Amount	$ 1,234,271	$ 1,213,609
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	350,350	341,529
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(266,543)	(260,045)
Backlog [Member]
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	2,899	2,875
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(2,469)	(2,375)
Client Relationships [Member]
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	313,595	305,178
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(238,245)	(231,902)
Client Contracts [Member]
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	15,339	15,366
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(15,339)	(15,366)
Trademarks and Trade Names [Member]
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	5,380	5,326
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(4,949)	(4,821)
Standard Operating Procedures [Member]
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	2,753	2,751
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(1,339)	(863)
Other Identifiable Intangible Assets [Member]
Other intangible assets
Other intangible assets subject to amortization, Gross Carrying Amount	10,384	10,033
Other intangible assets subject to amortization, Accumulated Amortization & Impairment Loss	(4,202)	(4,718)
Research Models [Member]
Other intangible assets
Other intangible assets not subject to amortization, Gross Carrying Amount	$ 3,438	$ 3,438