Income (loss) per share Schedule of the computation of basic and diluted net income (loss) per share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Annual dividend rate			8.00%
Net income (loss)	$ 1,181	$ (1,497)	$ 345	$ (1,342)
Less: undistributed earnings allocated to preferred stockholders	(1,078)	0	(345)	0
Net income (loss) attribuatble to common stockholders	$ 103	$ (1,497)	$ 0	$ (1,342)
Weighted-average shares used to compute basic net income (loss) per common share	21,738	3,313	12,700	3,164
Weighted average shares used to compute dluted income (loss) per common share	24,520	3,313	15,421	3,164
Basic and diluted net income (loss) per common share	$ 0.00	$ (0.45)	$ 0.00	$ (0.42)
Employee stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Employee stock options	2,698	0	2,622	0
Stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Employee stock options	84	0	99	0