Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ 469,577			$ 469,577
Other Comprehensive Income (Loss), Net of Tax	$ 98	109	$ 84	$ 78
Ending balance	435,024				435,024
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(21,814)		(20,149)	(21,814)	$ (20,149)
Amounts reclassified from accumulated other comprehensive loss					39	(9)
Income tax benefit					(2)	(5)
Net other comprehensive income					41	(4)
Tax benefit and Translation adjustment related to adoption of ASU	(2,707)				(2,707)
Ending balance	(24,480)		(20,153)		(24,480)	(20,153)
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(6,210)		(6,543)	(6,210)	(6,543)
Amounts reclassified from accumulated other comprehensive loss					166	166
Net other comprehensive income					166	166
Ending balance	(6,044)		(6,377)		(6,044)	(6,377)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(28,024)		(26,692)	(28,024)	(26,692)
Amounts reclassified from accumulated other comprehensive loss					205	157
Income tax benefit					(2)	(5)
Net other comprehensive income					207	162
Other Comprehensive Income (Loss), Net of Tax	98	$ 109	84	$ 78
Tax benefit and Translation adjustment related to adoption of ASU	(2,707)				(2,707)
Ending balance	$ (30,524)		$ (26,530)		$ (30,524)	$ (26,530)