CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accounts receivable, reserve for doubtful accounts	$ 7,116	$ 6,878
Property, plant and equipment, accumulated depreciation	$ 57,940	$ 54,014
Preferred stock, par value (in usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized	47,500,000	47,500,000
Common stock, shares issued	23,295,541	23,093,338
Treasury stock, shares	4,586,105	4,437,428