CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 3,008	$ 2,440
Shareholders' equity:
Preferred stock, authorized (in shares)	1,000,000
Preferred stock, issued (in shares)	0
Common stock, par value (in dollars per share)	$ 0.10
Common stock, shares authorized (in shares)	100,000,000
Common stock, shares issued (in shares)	29,134,244	28,969,244
Common stock held in treasury, shares (in shares)	11,479,279	10,670,693