Fair value measurement - additional information (Detail) (USD $)					3 Months Ended		9 Months Ended
	Sep. 28, 2014	Dec. 31, 2013	Sep. 28, 2014 Minimum	Sep. 28, 2014 Maximum	Sep. 28, 2014 Regulatory and Sales Milestones	Sep. 29, 2013 Regulatory and Sales Milestones	Sep. 28, 2014 Regulatory and Sales Milestones	Sep. 29, 2013 Regulatory and Sales Milestones
Fair Value Measurements [Line Items]
Reversal of contingent consideration liabilities					$ 1,500,000	$ 4,400,000	$ 8,200,000	$ 12,400,000
Fair value of contingent consideration liability associated with future milestone			0	56,500,000
Fair value measurement with unobservable inputs reconciliations liability value	12,643,000	20,313,000
Current Portion Of Contingent Consideration	2,957,000	4,131,000
Other liabilities	$ 9,600,000