CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts and disallowed sales (in dollars)	$ 25,485	$ 21,379
Patents and other intangible assets, accumulated amortization (in dollars)	$ 23,974	$ 20,643
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	36,031,041	35,617,884
Common stock, shares outstanding	36,031,041	35,617,884
Treasury stock, shares	141,154	141,154