Consolidated Balance Sheets Balance Sheet (Paranthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Allowance for doubtful accounts	$ 2,886	$ 43,961
Equity:
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	75,000	75,000
Common stock, shares issued	55,089	53,675
Common stock, shares outstanding	52,584	51,360
Common stock in treasury, at cost	1,932	1,932