Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Consolidated Balance Sheets
Receivables, allowance for doubtful accounts	$ 9,510	$ 10,084
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	95,065,638	95,065,638
Common stock, shares outstanding	57,608,088	57,337,720
Treasury stock, shares	37,457,550	37,727,918