Net Income Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
Net income (in dollars)	$ 3,712	$ 3,225	$ 6,290	$ 5,287
Denominator:
Weighted-average shares of common stock outstanding used in the calculation of basic net income per share	30,580,000	29,491,000	30,233,000	29,311,000
Effect of dilutive securities:
Weighted-average shares of common stock outstanding used in the calculation of diluted net income per share	32,578,000	30,808,000	32,095,000	30,661,000
Basic net income per share (in dollars per share)	$ 0.12	$ 0.11	$ 0.21	$ 0.18
Diluted net income per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.20	$ 0.17
Weighted-average shares of common stock outstanding but not included in computation of diluted net income per share	87,000	156,000	116,000	147,000
Options to purchase common stock
Effect of dilutive securities:
Effect of dilutive securities (in shares)	1,844,000	1,267,000	1,758,000	1,318,000
Restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (in shares)	154,000	50,000	104,000	32,000