CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
CONSOLIDATED BALANCE SHEETS [Abstract]
Accounts receivable, reserves	$ 10,258	$ 12,920
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	220,000,000	220,000,000
Common stock, shares issued	117,025,000	115,113,000
Treasury stock, at cost, shares	2,219,000	1,498,000