Segment Information - Goodwill and Total Assets (Details) (USD $) In Thousands, unless otherwise specified	Sep. 28, 2014	Dec. 31, 2013	Sep. 29, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Goodwill	$ 177,820	$ 136,152	$ 135,184	$ 131,320
Total Assets	1,439,516	1,426,084
Industry [Member]
Segment Reporting Information [Line Items]
Goodwill	97,598	51,532
Total Assets	403,355	297,987
Science [Member]
Segment Reporting Information [Line Items]
Goodwill	80,222	84,620
Total Assets	346,578	365,571
Corporate Eliminations [Member]
Segment Reporting Information [Line Items]
Total Assets	$ 689,583	$ 762,526