Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Allowances for doubtful accounts	$ 1,500	$ 1,497
Stockholders' equity:
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	41,070,216	40,925,619
Treasury stock, shares	4,008,963	4,008,963
Series B Preferred Stock
Stockholders' equity:
Preferred stock, unlimited shares authorized	unlimited shares	unlimited shares
Preferred stock, shares outstanding	0	0