Net Income per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Numerator:
Continuing operations	$ 28,331	$ 24,319	$ 20,774
Discontinued operation	1,839	(166)	16,109
Net income	$ 30,170	$ 24,153	$ 36,883
Denominator:
Denominator for basic net income per share-weighted average shares outstanding	51,797,000	51,535,000	50,899,000
Dilutive common equivalent shares:
Employee stock options and other (in shares)	2,288,000	2,941,000	2,010,000
Denominator for diluted net income per share- weighted average shares outstanding, assuming exercise of potential dilutive common shares	54,085,000	54,476,000	52,909,000
Basic net income per share:
Continuing operations (in dollars per share)	$ 0.55	$ 0.47	$ 0.41
Discontinued operation (in dollars per share)	$ 0.04		$ 0.32
Total operations (in dollars per share)	$ 0.58	$ 0.47	$ 0.72
Diluted net income per share:
Continuing operations (in dollars per share)	$ 0.52	$ 0.45	$ 0.39
Discontinued operation (in dollars per share)	$ 0.03		$ 0.30
Total operations (in dollars per share)	$ 0.56	$ 0.44	$ 0.70
Antidilutive securities excluded from computation of earnings per share (in shares)	2,100,000	1,800,000	3,800,000