Consolidated Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Allowance for doubtful trade accounts receivable	$ 10,032	$ 9,939
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	72,389,330	72,713,920
Treasury stock, shares	8,144,206	7,819,616