Net Income Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator:
Continuing operations	$ 30,231	$ 28,331	$ 24,319
Discontinued operation	184	1,839	(166)
Net income	$ 30,415	$ 30,170	$ 24,153
Denominator:
Denominator for basic net income (loss) per share-weighted average shares outstanding	50,614,000	51,797,000	51,535,000
Dilutive common equivalent shares:
Employee stock options and other (in shares)	1,811,000	2,288,000	2,941,000
Denominator for diluted net income (loss) per share- weighted average shares outstanding, assuming exercise of potential dilutive common equivalent shares	52,425,000	54,085,000	54,476,000
Basic net income per share:
Continuing operations (in dollars per share)	$ 0.60	$ 0.55	$ 0.47
Discontinued operation (in dollars per share)		$ 0.04
Total operations (in dollars per share)	$ 0.60	$ 0.58	$ 0.47
Diluted net income per share:
Continuing operations (in dollars per share)	$ 0.58	$ 0.52	$ 0.45
Discontinued operation (in dollars per share)		$ 0.03
Total operations (in dollars per share)	$ 0.58	$ 0.56	$ 0.44
Antidilutive securities excluded from computation of earnings per share (in shares)	3,200,000	2,100,000	1,800,000