Significant Accounting Policies (Details 7) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Allocation of stock-based compensation expense
Stock-based compensation expense	$ 7,708,000	$ 2,636,000	$ 14,777,000	$ 5,505,000
Stock option [Member]
Allocation of stock-based compensation expense
Unrecognized estimated non-cash stock-based compensation expense	29,000,000		29,000,000
Weighted average period of amortization			1 year 3 months 18 days
RSUs [Member]
Allocation of stock-based compensation expense
Vesting period			4 years
Unrecognized estimated non-cash stock-based compensation expense	13,200,000		13,200,000
Weighted average period of amortization			1 year 9 months 18 days
RSUs [Member] | Employees
Allocation of stock-based compensation expense
Weighted-average grant date fair value (in dollars per share)			$ 46.49
RSUs [Member] | Board of Directors [Member]
Allocation of stock-based compensation expense
Weighted-average grant date fair value (in dollars per share)			$ 49.09
Research, development and patent expenses
Allocation of stock-based compensation expense
Stock-based compensation expense	6,401,000	2,252,000	12,274,000	4,798,000
General and administrative
Allocation of stock-based compensation expense
Stock-based compensation expense	$ 1,307,000	$ 384,000	$ 2,503,000	$ 707,000