Segment and Geographic Information - Segment Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Sales to external customers	$ 927,454	$ 891,738	$ 826,426
Gross profit	438,785	415,630	367,366
Industry [Member]
Segment Reporting Information [Line Items]
Sales to external customers	427,731	433,424	376,533
Gross profit	222,675	220,267	185,156
Science [Member]
Segment Reporting Information [Line Items]
Sales to external customers	499,723	458,314	449,893
Gross profit	216,110	195,363	182,210
Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Concentration Risk Number of Customers Accounting For More Than Ten Percent of Revenue		0	0
Sales to external customers		0	0
Customer Concentration Risk [Member] | Industry [Member]
Segment Reporting Information [Line Items]
Concentration Risk Number of Customers Accounting For More Than Ten Percent of Revenue	1
Concentration Risk, Percentage	10.40%
Sales to external customers	$ 96,000