Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Income Per Share [Abstract]
Net income	$ 4,376	$ 5,142	$ 3,603	$ 2,986	$ 2,721	$ 3,466	$ 2,767	$ 1,793	$ 16,107	$ 10,747	$ 6,480
Shares used in computing basic net income per share									29,536	27,745	26,856
Stock options									194	279	659
Warrants										5	7
Restricted stock subject to vesting									621	578	774
Contingently issuable shares									81	222
Shares issuable for acquisition consideration									654	355	8
Shares used in computing diluted net income per share									31,086	29,184	28,304
Basic net income per share	$ 0.14	$ 0.17	$ 0.12	$ 0.10	$ 0.10	$ 0.12	$ 0.10	$ 0.07	$ 0.54	$ 0.39	$ 0.24
Diluted net income per share	$ 0.14	$ 0.16	$ 0.12	$ 0.10	$ 0.09	$ 0.12	$ 0.10	$ 0.06	$ 0.52	$ 0.37	$ 0.23
Anti-dilutive options and restricted stock not included in the calculation of diluted net income per share									12	278	538