Other Comprehensive Loss - Related Tax Effects Allocated to Each Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Equity [Abstract]
Amortization of actuarial losses, before tax amount	$ (804)	$ (506)
Derivative instruments	339	0
Cumulative translation adjustment, before tax amount	104	1,470
Total other comprehensive income (loss), before tax amount	(361)	964
Amortization of actuarial losses, tax	155	168
Derivative instrument, tax	0	0
Cumulative translation adjustment, tax	0	0
Total other comprehensive income (loss), tax	155	168
Amortization of actuarial losses, after tax amount	(649)	(338)
Derivative instrument, after tax amount	339	0
Cumulative translation adjustment, after tax amount	104	1,470
Total other comprehensive income (loss)	$ (206)	$ 1,132