Significant Accounting Policies (Details 7) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Allocation of stock-based compensation expense
Stock-based compensation expense	$ 7,069,000	$ 2,869,000
Stock option [Member]
Allocation of stock-based compensation expense
Unrecognized estimated non-cash stock-based compensation expense	33,500,000
Weighted average period of amortization	1 year 4 months 24 days
RSUs [Member]
Allocation of stock-based compensation expense
Vesting period	4 years
Unrecognized estimated non-cash stock-based compensation expense	14,600,000
Weighted average period of amortization	2 years
RSUs [Member] | Employees
Allocation of stock-based compensation expense
Weighted-average grant date fair value (in dollars per share)	$ 47.66	$ 14.21
RSUs [Member] | Board of Directors [Member]
Allocation of stock-based compensation expense
Weighted-average grant date fair value (in dollars per share)	$ 49.09	$ 0
Research, development and patent expenses
Allocation of stock-based compensation expense
Stock-based compensation expense	5,873,000	2,546,000
General and administrative
Allocation of stock-based compensation expense
Stock-based compensation expense	$ 1,196,000	$ 323,000