Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Allowance for doubtful accounts	$ 1,926	$ 1,525
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.008	$ 0.008
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	30,766,517	30,506,252
Common stock, shares outstanding (in shares)	25,703,125	25,761,334
Treasury stock, shares of common stock (in shares)	5,063,392	4,744,918