Fair Value Measurements Fair Value Measurements (Details) (USD $)					3 Months Ended		9 Months Ended					3 Months Ended	9 Months Ended
	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member]	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2013 Forward Contracts [Member]	Aug. 31, 2013 Forward Contracts [Member]	Sep. 30, 2013 Research and Development Expense [Member] Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2013 Research and Development Expense [Member] Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount										$ 49,200,000	$ 39,500,000
Cash equivalent money market funds (Level 1)	322,866,000	151,066,000
Restricted cash money market funds (Level 1)	2,681,000	2,680,000
Foreign currency forward contracts (Level 2)			1,167,000	0
Long-lived assets held for use or disposal (Level 3)					1,055,000		1,055,000		868,000
Losses on long-lived assets held for use or disposal (Level 3)					$ 578,000	$ 250,000	$ 1,446,000	$ 586,000				$ 500,000	$ 800,000