Fair Value (Details) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2011 USD ($)	Sep. 24, 2011 USD ($)	Jun. 25, 2011 USD ($)	Sep. 24, 2011 USD ($) increment segment month subsidiaries Y	Dec. 25, 2010 USD ($)	Sep. 14, 2010 EUR (€)	Sep. 14, 2010 CAD	Sep. 24, 2011 Time deposits Recurring basis Significant Other Observable Inputs Level 2 USD ($)	Dec. 25, 2010 Time deposits Recurring basis Significant Other Observable Inputs Level 2 USD ($)	Sep. 24, 2011 Time deposits Recurring basis Assets at Fair Value USD ($)	Dec. 25, 2010 Time deposits Recurring basis Assets at Fair Value USD ($)	Sep. 24, 2011 Auction rate securities Recurring basis Significant Unobservable Inputs Level 3 USD ($)	Dec. 25, 2010 Auction rate securities Recurring basis Significant Unobservable Inputs Level 3 USD ($)	Sep. 24, 2011 Auction rate securities Recurring basis Assets at Fair Value USD ($)	Dec. 25, 2010 Auction rate securities Recurring basis Assets at Fair Value USD ($)	Sep. 24, 2011 Recurring basis Significant Other Observable Inputs Level 2 USD ($)	Dec. 25, 2010 Recurring basis Significant Other Observable Inputs Level 2 USD ($)	Sep. 24, 2011 Recurring basis Significant Unobservable Inputs Level 3 USD ($)	Dec. 25, 2010 Recurring basis Significant Unobservable Inputs Level 3 USD ($)	Sep. 24, 2011 Recurring basis Assets at Fair Value USD ($)	Dec. 25, 2010 Recurring basis Assets at Fair Value USD ($)
Fair market value hedge contract
Notional amount of Canadian dollars purchased							62,637
Notional amount of Euros sold						46,940
Settlement amount on termination of hedge	4,008
Number of subsidiaries for which entity entered into forward foreign currency contract to hedge foreign exchange impact of intercompany loan				2
Proceeds from life insurance policies related to a former officer			9,500
Tax exempt gain from life insurance policies		7,710	7,710
Fair value of the contingent consideration attributable to the acquisition of the Systems Pathology Company, LLC (SPC)																		4,392	5,365	4,392	5,365
Reduction amount of fair value of the contingent consideration attributable to the acquisition of the Systems Pathology Company, LLC (SPC)			1,206
Assets and liabilities measured at fair value on a recurring basis
Fair value of life policies		24,174		24,174	31,054											18,690	25,609			18,690	25,609
Hedge contract																(45)	419			(45)	419
Total assets								6,188	9,834	6,188	9,834	11,070	11,377	11,070	11,377	24,833	35,862	11,070	11,377	35,903	47,239
Contingent consideration																		4,392	5,365	4,392	5,365
Total liabilities																		$ 4,392	$ 5,365	$ 4,392	$ 5,365
Contingent consideration probability adjustment rate, low end of range (as a percent)				5.00%
Contingent consideration probability adjustment rate, high end of range (as a percent)				70.00%
Contingent consideration discount rate (as a percent)				18.00%