Restructuring Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 28, 2013	Sep. 28, 2013	Sep. 28, 2013	Sep. 29, 2012
Restructuring Cost and Reserve [Line Items]
Accelerated depreciation estimate	$ 7,000	$ 6,766
Severance and Retention Costs
Balance, beginning of period	2,610		3,636	3,374
Expense			1,058	1,881
Payments for Restructuring			(2,084)	(1,415)
Balance, end of period		2,610	2,610	3,840
Severance and retention costs, current		1,197	1,197
Severance and retention costs, noncurrent		1,413	1,413
Severance and retention costs			1,058	1,881
Research Models and Services [Member]
Severance and Retention Costs
Severance and retention costs			811	934
Preclinical Services [Member]
Severance and Retention Costs
Severance and retention costs			247	947
Cost of Sales [Member]
Severance and Retention Costs
Severance and retention costs			989	936
General and Administrative Expense [Member]
Severance and Retention Costs
Severance and retention costs			$ 69	$ 945