Other Comprehensive Loss - Related Tax Effects Allocated to Each Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity [Abstract]
Amortization of actuarial losses, before tax amount	$ (2,186)	$ (1,230)	$ (380)	$ (2,500)
Derivative instruments	(515)		(193)
Cumulative translation adjustment, before tax amount	(3,388)	(1,529)	(3,048)	(5,363)
Total other comprehensive income (loss), before tax amount	(6,089)	(2,759)	(3,621)	(7,863)
Amortization of actuarial losses, tax	91	170	(628)	508
Derivative instrument, tax	0		0
Cumulative translation adjustment, tax	0	0	0	0
Total other comprehensive income (loss), tax	91	170	(628)	508
Amortization of actuarial losses, after tax amount	(2,095)	(1,060)	(1,008)	(1,992)
Derivative instrument, after tax amount	(515)	0	(193)	0
Cumulative translation adjustment, after tax amount	(3,388)	(1,529)	(3,048)	(5,363)
Total other comprehensive income (loss)	$ (5,998)	$ (2,589)	$ (4,249)	$ (7,355)