Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 763	$ 724
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	40,843,435	39,024,337
Common stock, shares outstanding (in shares)	31,341,276	30,825,123
Treasury stock, shares (in shares)	9,512,545	8,199,214