Consolidated Balance Sheets Parenthetical $ in Thousands	Sep. 30, 2019 USD ($) shares	Sep. 30, 2019 € / shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2018 € / shares
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts | $	$ 2,858		$ 2,650
Preferred stock, par value per share | € / shares		€ 0.02		€ 0.02
Preferred stock, shares authorized	6,000,000		6,000,000
Preferred stock, shares issued	0		0
Preferred stock, shares outstanding	0		0
Common stock, par value per share | € / shares		€ 0.02		€ 0.02
Common stock, shares authorized	200,000,000		200,000,000
Common stock, shares, issued	44,796,252		44,796,252
Common shares, outstanding	44,374,852		44,316,845
Treasury stock, shares	421,400		479,407