Fair Value Measurements (Details) (USD $)				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Convertible senior notes due 2016	Aug. 31, 2009 Convertible senior notes due 2016	Dec. 31, 2012 Auction rate securities	Dec. 31, 2012 Fair Value, Measurements, Recurring As reflected on the balance sheet	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet	Dec. 31, 2012 Fair Value, Measurements, Recurring As reflected on the balance sheet Money market funds	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet Money market funds	Dec. 31, 2012 Fair Value, Measurements, Recurring As reflected on the balance sheet Corporate and financial institutions debt	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet Corporate and financial institutions debt	Dec. 31, 2012 Fair Value, Measurements, Recurring As reflected on the balance sheet Auction rate securities	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet Auction rate securities	Dec. 31, 2012 Fair Value, Measurements, Recurring As reflected on the balance sheet U.S. government agencies	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet U.S. government agencies	Dec. 31, 2012 Fair Value, Measurements, Recurring As reflected on the balance sheet U.S. treasury bills	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet U.S. treasury bills	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet Municipal bonds	Dec. 31, 2011 Fair Value, Measurements, Recurring As reflected on the balance sheet Foreign currency option contracts not designated as hedges	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 1	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 1	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 1 Money market funds	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 1 Money market funds	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 1 U.S. treasury bills	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 1 U.S. treasury bills	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 2	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 2	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 2 Corporate and financial institutions debt	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 2 Corporate and financial institutions debt	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 2 U.S. government agencies	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 2 U.S. government agencies	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 2 Municipal bonds	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 2 Foreign currency option contracts not designated as hedges	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 3	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 3	Dec. 31, 2012 Fair Value, Measurements, Recurring Level 3 Auction rate securities	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 3 Auction rate securities	Dec. 31, 2012 Fair Value, Measurements, Recurring Total fair value	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value	Dec. 31, 2012 Fair Value, Measurements, Recurring Total fair value Money market funds	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value Money market funds	Dec. 31, 2012 Fair Value, Measurements, Recurring Total fair value Corporate and financial institutions debt	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value Corporate and financial institutions debt	Dec. 31, 2012 Fair Value, Measurements, Recurring Total fair value Auction rate securities	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value Auction rate securities	Dec. 31, 2012 Fair Value, Measurements, Recurring Total fair value U.S. government agencies	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value U.S. government agencies	Dec. 31, 2012 Fair Value, Measurements, Recurring Total fair value U.S. treasury bills	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value U.S. treasury bills	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value Municipal bonds	Dec. 31, 2011 Fair Value, Measurements, Recurring Total fair value Foreign currency option contracts not designated as hedges
Assets:
Total					$ 374,409,000	$ 559,360,000	$ 19,297,000	$ 30,800,000	$ 229,053,000	$ 303,799,000	$ 8,323,000	$ 22,102,000	$ 88,514,000	$ 147,445,000	$ 29,222,000	$ 40,328,000	$ 14,420,000	$ 466,000	$ 48,519,000	$ 71,128,000	$ 19,297,000	$ 30,800,000	$ 29,222,000	$ 40,328,000	$ 317,567,000	$ 466,130,000	$ 229,053,000	$ 303,799,000	$ 88,514,000	$ 147,445,000	$ 14,420,000	$ 466,000	$ 8,323,000	$ 22,102,000	$ 8,323,000	$ 22,102,000	$ 374,409,000	$ 559,360,000	$ 19,297,000	$ 30,800,000	$ 229,053,000	$ 303,799,000	$ 8,323,000	$ 22,102,000	$ 88,514,000	$ 147,445,000	$ 29,222,000	$ 40,328,000	$ 14,420,000	$ 466,000
Liabilities:
Liability for contingent consideration, current and non-current					149,163,000	159,990,000																											149,163,000	159,990,000			149,163,000	159,990,000
Convertible senior notes due 2016 (face value $230,000)					174,404,000	162,893,000																			468,533,000	303,255,000											468,533,000	303,255,000
Total					323,567,000	322,883,000																			468,533,000	303,255,000							149,163,000	159,990,000			617,696,000	463,245,000
Face value	230,000,000	230,000,000	230,000,000
Discount rates used in the cash flow analysis (as a percent)				2.00%
Change in the auction rate securites valuation as a result of a 1% increase or decrease in the discount rate				$ 400,000
Percent change to evaluate change in the auction rate securities valuation				1.00%
Expected holding period				5 years 1 month 17 days
Change in holding period used to evaluate the effect on auction rate securities valuation (in years)				1 year