Acquisitions (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 01, 2012	Apr. 03, 2011
Contingent compensation expenses
Total contingent compensation expense	$ 3,092	$ 2,124
Research and Development Expense [Member]
Contingent compensation expenses
Total contingent compensation expense	732	1,436
Selling General and Administrative Expense [Member]
Contingent compensation expenses
Total contingent compensation expense	$ 2,360	$ 688