Industry Segment Information (Schedule of Sales and Operating Income by Operating Segment, Excluding Discontinued Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 02, 2011	Oct. 03, 2010	Oct. 02, 2011 years segments days	Oct. 03, 2010
Segment Reporting Information [Line Items]
Number of operating segments			2
Sales	$ 453,740	$ 419,143	$ 1,381,095	$ 1,234,376
Operating income (loss) from continuing operations	34,208	41,417	111,040	105,280
Interest and other expense (income), net	3,916	6,680	13,943	(11,851)
Income from continuing operations before income taxes	30,292	34,737	97,097	117,131
Human Health [Member]
Segment Reporting Information [Line Items]
Sales	207,419	194,510	628,669	580,568
Operating income (loss) from continuing operations	26,672	24,980	74,994	72,606
Environmental Health [Member]
Segment Reporting Information [Line Items]
Sales	246,321	224,633	752,426	653,808
Operating income (loss) from continuing operations	13,641	26,109	63,462	61,813
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations	$ (6,105)	$ (9,672)	$ (27,416)	$ (29,139)