Income Taxes - Schedule of Deferred Income Taxes (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Accrued expenses	$ 760	$ 1,363
Allowance for doubtful accounts	184	134
Contract overrun reserves	1,776	4,412
Deferred compensation	507	491
Employment-related accruals	2,888	2,463
Environmental reserves	769	772
Federal tax credit carryforwards	4,234	7,031
Inventory reserves	2,313	2,703
Investment in common stock	0	297
Pension obligation	4,002	3,299
State net operating loss carryforwards	63	1,402
State tax credit carryforwards	6,585	5,937
Stock-based compensation	1,950	2,165
Workers’ compensation	122	133
Other	2,098	1,595
Total gross deferred tax assets	28,251	34,197
Valuation allowance	(6,607)	(7,477)
Total gross deferred tax assets, net of valuation allowance	21,644	26,720
Deferred tax liabilities:
Depreciation	(13,167)	(11,802)
Goodwill	(3,909)	(3,632)
Intangibles	(35,071)	(37,891)
Prepaid insurance	(626)	(514)
Section 481(a) adjustment	0	(682)
Unbilled receivables	(2)	0
Total gross deferred tax liabilities	(52,775)	(54,521)
Net deferred tax liabilities	$ (31,131)	$ (27,801)