Industry Segment and Geographic Area Information Schedule of Total Assets by Segment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013	Dec. 30, 2012
Schedule of Total Assets, by segment [Line Items]
Assets	$ 4,134,075	$ 3,946,712
Human Health [Member]
Schedule of Total Assets, by segment [Line Items]
Assets	2,645,411	2,692,809	2,700,565
Environmental Health [Member]
Schedule of Total Assets, by segment [Line Items]
Assets	1,453,683	1,213,801	1,153,444
Corporate [Member]
Schedule of Total Assets, by segment [Line Items]
Assets	34,981	34,271	33,952
Net current and long-term assets of discontinued operations [Member]
Schedule of Total Assets, by segment [Line Items]
Assets	0	5,831	13,801
Total assets [Member]
Schedule of Total Assets, by segment [Line Items]
Assets	$ 4,134,075	$ 3,946,712	$ 3,901,762