Net Income (Loss) Per Share Attributable to Common Stockholders (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Net income	$ 1,309	$ 1,667	$ 1,579	$ 1,105
Net income attributable to participating securities	(2)	(1,252)	(2)	(841)
Net income attributable to common stockholders - basic	1,307	415	1,577	264
Undistributed earnings allocated to participating securities	1	1,249	0	839
Net income attributable to common stockholders - diluted	$ 1,308	$ 1,664	$ 1,577	$ 1,103
Denominator:
Weighted - average shares used in computing net income per share attributable to common stockholders - basic (shares)	32,088	5,843	31,789	5,540
Effect of potentially dilutive securities: Convertible preferred stock	0	17,597	0	17,597
Effect of potentially dilutive securities: Common stock options	4,159	3,105	3,915	2,829
Effect of potentially dilutive securities: Contingently issuable shares		0	0	6
Weighted - average shares used in computing net income per share attributable to common stockholders - diluted (shares)	36,247	26,545	35,704	25,972
Basic (USD per share)	$ 0.04	$ 0.07	$ 0.05	$ 0.05
Diluted (USD per share)	$ 0.04	$ 0.06	$ 0.04	$ 0.04
Antidilutive Securities
Antidilutive securities	394	1,108	956	1,031
Stock Options
Antidilutive Securities
Antidilutive securities	394	1,108	956	1,031