Stock-based compensation and awards (Details) (USD $)	9 Months Ended
	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Shares available for grant, Beginning Balances	1,343,978
Number of shares Beginning Balances	4,505,153
Options granted, Shares available for grant	(790,364)
Options granted, Number of shares	790,364
Options exercised, Shares available for grant
Options exercised, Number of shares	(216,035)
Options cancelled, Shares available for grant	197,371
Options cancelled, Number of shares	(197,371)
Options retired - 2001 Plan	(120,874)
Options retired - 2001 Plan, Number of Shares
Shares available for grant, Ending Balances	630,111
Number of shares Ending Balances	4,882,111
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price
Options, Outstanding, Weighted average exercise price, Beginning Balance	$ 4.25
Options, Grants in Period, Weighted average exercise price	$ 15.11
Options, Exercises in Period, Weighted average exercise price	$ 2.36
Options, Cancelled in Period, Weighted average exercise price	$ 7.28
Options retired - 2001 Plan, Weighted average exercise price
Options, Outstanding, Weighted average exercise price, Ending Balance	$ 5.98