Industry Segment Information (Schedule of Sales and Operating Income by Operating Segment, Excluding Discontinued Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016
Segment Reporting Information [Line Items]
Product revenue	$ 355,001	$ 356,975	$ 688,715	$ 681,328
Service revenue	191,961	179,267	372,362	352,930
Total revenue	546,962	536,242	1,061,077	1,034,258
Operating income (loss) from continuing operations	75,997	66,266	127,576	126,843
Interest and other expense, net	5,205	5,393	16,801	16,479
Income from continuing operations before income taxes	70,792	60,873	110,775	110,364
Change in allocation of functional Costs, Effect on operating income (loss)		2,481		6,181
Human Health [Member]
Segment Reporting Information [Line Items]
Product revenue			442,450	455,919
Service revenue			302,438	282,032
Total revenue			744,888	737,951
Operating income (loss) from continuing operations			82,060	81,086
Environmental Health [Member]
Segment Reporting Information [Line Items]
Product revenue			246,265	225,409
Service revenue			69,924	70,898
Total revenue			316,189	296,307
Operating income (loss) from continuing operations			71,051	71,614
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations	(13,125)	(13,191)	$ (25,535)	$ (25,857)
Diagnostics [Member]
Segment Reporting Information [Line Items]
Product revenue	127,711	120,462
Service revenue	36,123	34,276
Total revenue	163,834	154,738
Operating income (loss) from continuing operations	37,641	37,840
Discovery & Analytical Solutions [Member]
Segment Reporting Information [Line Items]
Product revenue	227,290	236,513
Service revenue	155,838	144,991
Total revenue	383,128	381,504
Operating income (loss) from continuing operations	$ 51,481	$ 41,617