Adoption of Accounting Standards Codification 606 - Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 10,263		$ 2,150	$ 7,432	$ 5,454
Accounts receivable, net of allowance for doubtful accounts of $1,135 at December 31, 2018	67,819		74,064
Contract assets	86,665	$ 68,739	0
Inventories	101,125	83,159	122,161
Production cost of contracts	11,679		11,204
Other current assets	9,839		11,435
Total Current Assets	287,390		221,014
Property and Equipment, Net	107,045		110,252
Goodwill	136,057		117,435
Intangibles, Net	112,092		114,693
Non-Current Deferred Income Taxes	308	166	261
Other Assets	5,251		3,098
Total Assets	648,143		566,753
Current Liabilities
Accounts payable	69,274		51,907
Contract liabilities	17,145	24,460	0
Accrued liabilities	37,786	22,238	28,329
Current portion of long-term debt	2,330		0
Total Current Liabilities	126,535		80,236
Long-Term Debt, Less Current Portion	226,961		216,055
Non-Current Deferred Income Taxes	18,070	18,589	15,981
Other Long-Term Liabilities	19,752		18,898
Total Liabilities	391,318		331,170
Commitments and Contingencies (Notes 13, 16)
Equity [Abstract]
Common stock - $0.01 par value; 35,000,000 shares authorized; 11,417,863 and 11,332,841 shares issued and outstanding at December 31, 2018 and 2017, respectively	114		113
Additional paid-in capital	83,712		80,223
Retained earnings	180,356	170,029	161,364
Accumulated other comprehensive loss	(7,357)		(6,117)
Total Shareholders’ Equity	256,825		235,583	$ 212,103	$ 185,734
Total Liabilities and Shareholders’ Equity	648,143		566,753
Accounts receivable, allowance for doubtful accounts	1,135		868
Less accumulated depreciation	$ 154,840		$ 143,216
Common stock, par value (in dollars per share)	$ 0.01		$ 0.01
Common stock, shares authorized (in shares)	35,000,000		35,000,000
Common stock, shares issued (in shares)	11,417,863		11,332,841
Common Stock, shares outstanding (in shares)	11,417,863		11,332,841
Calculated under Revenue Guidance in Effect before Topic 606
Current Assets
Cash and cash equivalents	$ 10,263		$ 2,150
Accounts receivable, net of allowance for doubtful accounts of $1,135 at December 31, 2018	67,819
Contract assets	0		0
Inventories	158,652		122,161
Production cost of contracts	11,679
Other current assets	10,924
Total Current Assets	259,337
Property and Equipment, Net	107,045
Goodwill	136,057
Intangibles, Net	112,092
Non-Current Deferred Income Taxes	316		261
Other Assets	5,251
Total Assets	620,098
Current Liabilities
Accounts payable	69,274
Contract liabilities	0		0
Accrued liabilities	42,780		28,329
Current portion of long-term debt	2,330
Total Current Liabilities	114,384
Long-Term Debt, Less Current Portion	226,961
Non-Current Deferred Income Taxes	15,500		15,981
Other Long-Term Liabilities	19,752
Total Liabilities	376,597
Equity [Abstract]
Common stock - $0.01 par value; 35,000,000 shares authorized; 11,417,863 and 11,332,841 shares issued and outstanding at December 31, 2018 and 2017, respectively	114
Additional paid-in capital	83,712
Retained earnings	167,032		161,364
Accumulated other comprehensive loss	(7,357)
Total Shareholders’ Equity	243,501
Total Liabilities and Shareholders’ Equity	620,098
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Current Assets
Cash and cash equivalents	0		$ 0
Accounts receivable, net of allowance for doubtful accounts of $1,135 at December 31, 2018	0
Contract assets	(86,665)	68,739
Inventories	57,527	(39,002)
Production cost of contracts	0
Other current assets	1,085
Total Current Assets	(28,053)
Property and Equipment, Net	0
Goodwill	0
Intangibles, Net	0
Non-Current Deferred Income Taxes	8	(95)
Other Assets	0
Total Assets	(28,045)
Current Liabilities
Accounts payable	0
Contract liabilities	(17,145)	24,460
Accrued liabilities	4,994	(6,091)
Current portion of long-term debt	0
Total Current Liabilities	(12,151)
Long-Term Debt, Less Current Portion	0
Non-Current Deferred Income Taxes	(2,570)	2,608
Other Long-Term Liabilities	0
Total Liabilities	(14,721)
Equity [Abstract]
Common stock - $0.01 par value; 35,000,000 shares authorized; 11,417,863 and 11,332,841 shares issued and outstanding at December 31, 2018 and 2017, respectively	0
Additional paid-in capital	0
Retained earnings	(13,324)	$ 8,665
Accumulated other comprehensive loss	0
Total Shareholders’ Equity	(13,324)
Total Liabilities and Shareholders’ Equity	$ (28,045)