Consolidated Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Allowance for doubtful trade accounts receivable	$ 10,457	$ 10,154
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	80,533,536	80,533,536
Common stock, shares outstanding	72,869,626	72,847,576
Treasury stock, shares	7,663,910	7,685,960