Interim Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 13,011	$ 10,326
Common stock, par value (dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (shares)	20,000,000	20,000,000
Common stock, shares issued (shares)	6,690,000	6,592,000
Common stock, shares outstanding (shares)	6,458,000	6,361,000
Treasury stock, shares (shares)	232,000	232,000