Restatement - Consolidated Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Current Assets
Cash and cash equivalents	$ 45,627	$ 40,852	$ 43,751	$ 29,415	$ 48,814	$ 32,597	$ 33,510	$ 29,994	$ 46,537	$ 41,449
Accounts receivable (less allowance for doubtful accounts of $489 at December 31, 2013)	91,060	104,396	105,209	100,570	91,909	92,637	105,577	96,391
Inventories	142,842	145,468	142,201	148,895	140,507	148,524	147,826	148,462
Production cost of contracts	11,727	10,375	11,023	10,479	11,599	19,926	19,049	20,193
Deferred income taxes	13,783	15,185	12,929	15,340	12,669	8,711	9,152	13,309
Other current assets	23,702	21,930	21,600	22,662	28,083	24,971	18,022	12,773
Total Current Assets	328,741	338,206	336,713	327,361	333,581	327,366	333,136	321,122
Property and Equipment, Net	99,068	93,181	94,070	94,168	96,090	93,840	95,602	97,005
Goodwill	157,569	157,569	157,569	157,569	157,569	157,569	157,569	157,569
Intangibles, Net	155,104	157,694	160,285	162,875	165,465	168,188	170,911	173,633
Other Assets	7,117	7,657	8,660	9,320	9,940	11,779	12,310	13,217
Total Assets	747,599	754,307	757,297	751,293	762,645	758,742	769,528	762,546
Current Liabilities
Current portion of long-term debt	26	26	26	25	25	3,029	3,033	3,038
Accounts payable	58,979	55,083	53,749	53,973	58,111	49,668	50,864	50,481
Accrued liabilities	52,066	46,787	51,562	43,452	50,122	43,620	53,047	45,101
Total Current Liabilities	111,071	101,896	105,337	97,450	108,258	96,317	106,944	98,620
Long-Term Debt, Less Current Portion	290,026	310,157	317,664	325,171	332,677	340,184	347,690	355,196
Deferred Income Taxes	69,448	72,578	69,247	70,056	67,989	63,883	65,359	65,765
Other Long-Term Liabilities	20,484	16,558	17,156	18,622	19,450	21,797	22,600	22,939
Total Liabilities	491,029	501,189	509,404	511,299	528,374	522,181	542,593	542,520
Commitments and Contingencies
Shareholders' Equity
Common stock - $0.01 par value; 35,000,000 shares authorized; 10,960,054 shares issued at December 31, 2013	110	109	109	110	110	109	108	107
Treasury stock, at cost; 143,300 shares at December 31, 2013	0			(1,924)	(1,924)	(1,924)	(1,924)	(1,924)
Additional paid-in capital	72,206	70,930	68,704	69,404	68,909	69,046	66,578	65,508
Retained earnings	190,905	185,749	182,816	176,197	171,038	176,282	169,297	163,631
Accumulated other comprehensive loss	(6,651)	(3,670)	(3,736)	(3,793)	(3,862)	(6,952)	(7,124)	(7,296)
Total Shareholders’ Equity	256,570	253,118	247,893	239,994	234,271	236,561	226,935	220,026	215,217	195,640
Total Liabilities and Shareholders’ Equity	747,599	754,307	757,297	751,293	762,645	758,742	769,528	762,546
As Reported
Current Assets
Cash and cash equivalents		40,852	43,751	29,415	48,814	32,597	33,510	29,994	46,537	41,449
Accounts receivable (less allowance for doubtful accounts of $489 at December 31, 2013)		104,396	105,209	100,570	91,909	92,637	105,577	96,391
Inventories		145,468	142,201	148,895	140,507	148,524	148,906	149,402
Production cost of contracts		10,375	11,023	10,479	11,599	19,926	19,049	20,193
Deferred income taxes		13,664	11,513	13,836	10,850	7,110	7,016	11,077
Other current assets		20,444	20,602	21,664	27,085	23,505	18,005	12,756
Total Current Assets		335,199	334,299	324,859	330,764	324,299	332,063	319,813
Property and Equipment, Net		93,181	94,070	94,168	96,090	93,840	95,602	97,005
Goodwill		161,940	161,940	161,940	161,940	161,940	161,940	161,940
Intangibles, Net		157,694	160,285	162,875	165,465	168,188	170,911	173,633
Other Assets		7,657	8,660	9,320	9,940	11,779	12,310	13,217
Total Assets		755,671	759,254	753,162	764,199	760,046	772,826	765,608
Current Liabilities
Current portion of long-term debt		26	26	25	25	3,029	3,033	3,038
Accounts payable		55,083	53,749	53,973	58,111	49,668	50,864	50,481
Accrued liabilities		42,916	47,973	39,628	45,453	39,320	48,392	40,048
Total Current Liabilities		98,025	101,748	93,626	103,589	92,017	102,289	93,567
Long-Term Debt, Less Current Portion		310,157	317,664	325,171	332,677	340,184	347,690	355,196
Deferred Income Taxes		73,078	69,747	70,556	68,489	64,504	65,980	66,386
Other Long-Term Liabilities		16,858	17,456	18,922	19,750	22,097	22,900	23,239
Total Liabilities		498,118	506,615	508,275	524,505	518,802	538,859	538,388
Shareholders' Equity
Common stock - $0.01 par value; 35,000,000 shares authorized; 10,960,054 shares issued at December 31, 2013		109	109	110	110	109	108	107
Treasury stock, at cost; 143,300 shares at December 31, 2013				(1,924)	(1,924)	(1,924)	(1,924)	(1,924)
Additional paid-in capital		72,563	70,337	71,037	70,542	70,679	68,211	67,141
Retained earnings		188,551	185,929	179,457	174,828	179,332	174,696	169,192
Accumulated other comprehensive loss		(3,670)	(3,736)	(3,793)	(3,862)	(6,952)	(7,124)	(7,296)
Total Shareholders’ Equity		257,553	252,639	244,887	239,694	241,244	233,967	227,220
Total Liabilities and Shareholders’ Equity		755,671	759,254	753,162	764,199	760,046	772,826	765,608
Restatement Adjustment
Current Assets
Cash and cash equivalents		0	0	0	0	0	0	0	0	0
Accounts receivable (less allowance for doubtful accounts of $489 at December 31, 2013)		0	0	0	0	0	0	0
Inventories		0	0	0	0	0	(1,080)	(940)
Production cost of contracts		0	0	0	0	0	0	0
Deferred income taxes		1,521	1,416	1,504	1,819	1,601	2,136	2,232
Other current assets		1,486	998	998	998	1,466	17	17
Total Current Assets		3,007	2,414	2,502	2,817	3,067	1,073	1,309
Property and Equipment, Net		0	0	0	0	0	0	0
Goodwill		(4,371)	(4,371)	(4,371)	(4,371)	(4,371)	(4,371)	(4,371)		4,000
Intangibles, Net		0	0	0	0	0	0	0
Other Assets		0	0	0	0	0	0	0
Total Assets		(1,364)	(1,957)	(1,869)	(1,554)	(1,304)	(3,298)	(3,062)
Current Liabilities
Current portion of long-term debt		0	0	0	0	0	0	0
Accounts payable		0	0	0	0	0	0	0
Accrued liabilities		3,871	3,589	3,824	4,669	4,300	4,655	5,053
Total Current Liabilities		3,871	3,589	3,824	4,669	4,300	4,655	5,053
Long-Term Debt, Less Current Portion		0	0	0	0	0	0	0
Deferred Income Taxes		(500)	(500)	(500)	(500)	(621)	(621)	(621)
Other Long-Term Liabilities		(300)	(300)	(300)	(300)	(300)	(300)	(300)
Total Liabilities		3,071	2,789	3,024	3,869	3,379	3,734	4,132
Shareholders' Equity
Common stock - $0.01 par value; 35,000,000 shares authorized; 10,960,054 shares issued at December 31, 2013		0	0	0	0	0	0	0
Treasury stock, at cost; 143,300 shares at December 31, 2013				0	0	0	0	0
Additional paid-in capital		(1,633)	(1,633)	(1,633)	(1,633)	(1,633)	(1,633)	(1,633)
Retained earnings		(2,802)	(3,113)	(3,260)	(3,790)	(3,050)	(5,399)	(5,561)
Accumulated other comprehensive loss		0	0	0	0	0	0	0
Total Shareholders’ Equity		(4,435)	(4,746)	(4,893)	(5,423)	(4,683)	(7,032)	(7,194)
Total Liabilities and Shareholders’ Equity		$ (1,364)	$ (1,957)	$ (1,869)	$ (1,554)	$ (1,304)	$ (3,298)	$ (3,062)