Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 378,156
Balance	373,694
Minimum Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(20,149)	$ (22,268)
Amounts reclassified from accumulated other comprehensive loss	(9)	45
Income tax benefit	5
Net other comprehensive income (loss)	(4)	45
Balance	(20,153)	(22,223)
Other-Than-Temporary Impairment of Investment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(6,543)
Amounts reclassified from accumulated other comprehensive loss	166
Net other comprehensive income (loss)	166
Balance	(6,377)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(26,692)	(22,268)
Amounts reclassified from accumulated other comprehensive loss	157	45
Income tax benefit	5
Net other comprehensive income (loss)	162	45
Balance	$ (26,530)	$ (22,223)