Statements of Consolidated Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Comprehensive Income Net Of Tax [Abstract]
Net income	$ 6,735	$ 4,156	$ 12,263	$ 5,674
Other comprehensive income, net of tax
Foreign currency translation adjustment	(13,367)	2,810	(9,535)	8,282
Recognized net actuarial gain (net of tax provision of $29 and $49 for the three months ended June 30, 2018 and 2017, respectively, and net of tax provision of $59 and $93 for the six months ended June 30, 2018 and 2017, respectively.)	92	83	183	155
Other comprehensive income (loss), net of tax	(13,275)	2,893	(9,352)	8,437
Comprehensive income (loss)	$ (6,540)	$ 7,049	$ 2,911	$ 14,111