Employee Stock-Based Compensation - Stock Option Activity (Details) (USD $)	9 Months Ended
	Sep. 30, 2014
Number of Shares
Options Outstanding, beginning balance	5,160,086
Shares Granted	709,025
Shares Cancelled	(13,678)
Shares Exercised	(255,000)
Shares Expired
Options Outstanding, ending balance	5,600,433
Weighted Average Exercise Price Per Share
Options Outstanding, beginning balance	$ 3.45
Shares Granted	$ 15.78
Shares Cancelled	$ 13.06
Shares Exercised	$ 2.86
Shares Expired
Options Outstanding, ending balance	$ 5.01