CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Customer receivables, net of allowance for doubtful accounts of $3,724 and $4,039, respectively	$ 3,724	$ 4,039
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	65,778,891	65,460,014
Common stock, shares outstanding	49,431,178	49,339,552
Non-vesting restricted shares	725,252	841,610
Treasury shares	16,347,713	16,120,462