Equity Incentive Plans (Details) (USD $)	9 Months Ended
	Sep. 30, 2012
Option activity under its Stock Plans
Shares, Options outstanding, Beginning Balance	4,016,393
Shares, Options outstanding, Granted	1,508,070
Shares, Options outstanding, Exercised	(89,977)
Shares, Options outstanding, Forfeited	(37,527)
Shares, Options outstanding, Ending Balance	5,396,959
Weighted Average Exercise Price, Options outstanding, Beginning Balance	$ 4.89
Weighted Average Exercise Price, Granted	$ 13.47
Weighted Average Exercise Price, Exercised	$ 3.51
Weighted Average Exercise Price, Forfeited	$ 9.32
Weighted Average Exercise Price, Options outstanding, Ending Balances	$ 7.28
Shares, Options, Weighted Average Remaining Contractual Term	6 years 10 months 13 days
Shares, Options, Aggregate Intrinsic Value	$ 26,685,432