Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, allowances for doubtful accounts	$ 7,116	$ 6,217
Common stock, par value (in dollars per share)	$ 0.25	$ 0.25
Common stock, shares authorized	360,000,000	360,000,000
Common stock, shares issued	110,834,088	110,834,088
Treasury stock, shares	12,294,873	12,554,714