Income Taxes (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified	0 Months Ended		3 Months Ended	12 Months Ended				12 Months Ended		0 Months Ended		1 Months Ended
	Oct. 20, 2010	Jul. 29, 2010	Mar. 26, 2011	Dec. 31, 2011	Dec. 25, 2010	Dec. 26, 2009	Dec. 31, 2011 Investments in Foreign Subsidiaries that are Essentially Permanent in Duration [Member]	Dec. 25, 2010 Income Tax Expense [Member]	Dec. 25, 2010 Cumulated Translation Adjustment [Member]	Aug. 26, 2010 Accelerated stock repurchase program entered into on August 26, 2010	Jun. 12, 2006 2.25% Senior convertible debentures	Jun. 20, 2006 2.25% Senior convertible debentures	Dec. 31, 2011 2.25% Senior convertible debentures	Dec. 25, 2010 2.25% Senior convertible debentures
Income Tax Contingency [Line Items]
Pool of excess tax benefits				$ 10,580,000	$ 12,614,000
Tax detriment recorded to additional pain-in-capital related to exercise of stock options and vesting of restricted shares				802,000
Increase in valuation allowance				137,000
Valuation allowance				12,178,000	12,041,000
Income tax benefit associated with a tax loss incurred with the disposition of Phase I clinical business			11,111,000
Authorized amount of stock repurchase	750,000,000	500,000,000								300,000,000
Undistributed earnings of foreign subsidiaries, previously reinvested					229,792,000
Basis in foreign subsidiaries to be repatriated					63,640,000
Cost of repatriation of foreign earnings					10,334,000			15,264,000	(4,930,000)
Foreign earnings repatriated during the period					293,432,000
Termination fee				0	30,000,000	0
Earnings of non-U.S. subsidiaries considered indefinitely reinvested							106,504,000
Provision for U.S. income taxes							0
Aggregate principal amount											300,000,000		350,000,000
Additional principal amount issued												50,000,000
Net proceeds from issuance of debt											294,000,000	49,000,000
Interest rate on debt (as a percent)											2.25%	2.25%	2.25%	2.25%
Unamortized debt discount												$ 88,492,000	$ 21,533,000	$ 35,583,000
Warrants issued (in shares)				7.2
Original issue discount (OID) deduction period (in years)				7 years