Stockholders' Equity - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ (22,268)	$ (25,047)	$ (26,331)
Unrealized gains (losses) arising during period	(3,432)	2,599	1,920
Amounts reclassified from accumulated other comprehensive loss	60	180	88
Income tax expense	(1,052)		(724)
Other comprehensive income (loss), net of tax	(4,424)	2,779	1,284
Balance	(26,692)	(22,268)	(25,047)
Minimum Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(22,268)	(25,047)	(26,331)
Unrealized gains (losses) arising during period	3,111	2,599	1,920
Amounts reclassified from accumulated other comprehensive loss	60	180	88
Income tax expense	(1,052)		(724)
Other comprehensive income (loss), net of tax	2,119	2,779	1,284
Balance	(20,149)	(22,268)	(25,047)
Other-Than-Temporary Impairment of Investment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	0	0	0
Unrealized gains (losses) arising during period	(6,543)
Other comprehensive income (loss), net of tax	(6,543)
Balance	$ (6,543)	$ 0	$ 0