Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Assets
Allowance for doubtful accounts	$ 4,996	$ 3,174
Shareholders' equity
Common stock, par value
Common stock, shares issued	61,362,281	61,478,168
Common stock, shares outstanding	61,290,617	61,433,589
Number of treasury shares held in trust for future settlement of share based awards	71,664	44,579