Restatement of Previously issued Financial Statements and Financial Information (Consolidated Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Trade and other accounts receivable, allowance	$ 157	$ 341	$ 216	$ 281	$ 450	$ 451	$ 353	$ 209
Current assets:
Cash and cash equivalents	28,739	20,073	22,310	30,628	29,289	30,988	29,791	33,063	39,829	29,582
Accounts Receivable, Net, Current	33,420	38,816	34,334	32,523	27,973	30,007	32,201	26,214
Inventories	41,620	43,802	41,039	39,180	33,234	29,662	29,030	26,465
Prepaid expenses and other current assets	3,228	2,975	3,458	3,295	3,152	3,204	2,955	2,683
Total current assets	107,007	105,666	101,141	105,626	93,648	93,861	93,977	88,425
Property and equipment, net	36,235	35,806	33,275	31,922	28,541	26,985	24,952	22,257
Intangible assets, net	669	758	854	985	1,111	1,259	1,438	1,526
Goodwill	25,416	24,826	24,621	25,730	24,887	25,592	27,423	25,338	24,956
Pension asset	6,939	6,945	6,685	6,815	6,359	6,125	6,387	5,642
Other non-current assets	206	38	38	0	200	246	382	471
Total assets	176,472	174,039	166,614	171,078	154,746	154,068	154,559	143,659
Current liabilities:
Accounts payable and accrued liabilities	27,181	31,989	31,245	34,254	36,100	30,971	30,628	28,851
Accrued warranty	269	244	265	287	258	261	304	367
Accrued employee compensation	4,743	5,025	5,721	5,850	6,343	7,037	6,931	4,942
Deferred revenue	6,408	5,149	4,170	2,568	1,042
Short-term borrowings and current portion of long-term debt	9,452	9,844	10,224	10,649	5,431	3,409	3,685	3,470
Deferred tax liability	980	499	499	499	499	1,373	1,373	1,373
Total current liabilities	49,033	52,750	52,124	54,107	49,673	45,529	44,097	39,422
Deferred tax liability, long-term	1,384	962	952	944	933	1,166	1,166	1,166
Long-term debt, excluding current portion	83	25	35	47	68	2,292	2,504	2,282
Other long-term liabilities	1,039	699	750	778	3,028	3,028	3,070	3,049
Total liabilities	51,539	54,436	53,861	55,876	53,702	52,015	50,837	45,919
Commitments and contingencies (Note 12 and Note 14)
Stockholders’ equity:
Common stock, $0.10 par value per share, 40,000 shares authorized; 29,162 and 28,174 shares issued and outstanding at December 31, 2012 and 2011, respectively	2,913	2,915	2,911	2,910	2,815	2,797	2,780	2,779
Additional paid-in capital	267,623	267,069	266,225	265,414	252,907	252,525	250,341	249,558
Accumulated deficit	(158,134)	(161,000)	(166,229)	(166,260)	(165,308)	(165,823)	(166,392)	(166,192)
Accumulated other comprehensive income	12,531	10,619	9,846	13,138	10,630	12,554	16,993	11,595
Total stockholders’ equity	124,933	119,603	112,753	115,202	101,044	102,053	103,722	97,740	88,023	77,992
Total liabilities and stockholders’ equity	176,472	174,039	166,614	171,078	154,746	154,068	154,559	143,659
Scenario, Previously Reported [Member]
Current assets:
Cash and cash equivalents		20,073	22,310	30,628	29,289	30,988	29,791	33,063	39,829
Accounts Receivable, Net, Current		52,988	48,514	43,147	36,131	31,838	35,791	32,301
Inventories		31,930	30,217	30,606	27,232	27,965	26,911	22,913
Prepaid expenses and other current assets		2,829	3,299	3,158	3,125	3,191	2,939	2,657
Total current assets		107,820	104,340	107,539	95,777	93,982	95,432	90,934
Property and equipment, net		35,806	33,275	31,922	28,541	26,985	24,952	22,257
Intangible assets, net		758	854	985	1,111	1,259	1,438	1,526
Goodwill		24,826	24,621	25,730	24,887	25,592	27,423	25,338
Pension asset		6,945	6,685	6,815	6,359	6,125	6,387	5,642
Other non-current assets		79	94	59	261	246	382	471
Total assets		176,234	169,869	173,050	156,936	154,189	156,014	146,168
Current liabilities:
Accounts payable and accrued liabilities		32,025	31,205	34,239	36,103	29,862	30,582	28,842
Accrued warranty		244	265	287	258	261	304	367
Accrued employee compensation		5,025	5,721	5,850	6,243	7,037	6,931	4,942
Deferred revenue		764	1,096	812	1,042	2,478	1,176	419
Short-term borrowings and current portion of long-term debt		6,909	6,870	7,155	5,431	3,409	3,685	3,470
Deferred tax liability		499	499	499	499	1,373	1,373	1,373
Total current liabilities		45,466	45,656	48,842	49,576	44,420	44,051	39,413
Deferred tax liability, long-term		962	952	944	933	1,166	1,166	1,166
Long-term debt, excluding current portion		2,960	3,389	3,541	68	2,292	2,504	2,282
Other long-term liabilities		699	750	778	3,028	3,028	3,070	3,049
Total liabilities		50,087	50,747	54,105	53,605	50,906	50,791	45,910
Commitments and contingencies (Note 12 and Note 14)
Stockholders’ equity:
Common stock, $0.10 par value per share, 40,000 shares authorized; 29,162 and 28,174 shares issued and outstanding at December 31, 2012 and 2011, respectively		2,915	2,911	2,910	2,815	2,797	2,780	2,779
Additional paid-in capital		267,069	266,225	265,414	252,907	252,525	250,341	249,558
Accumulated deficit		(154,456)	(159,860)	(162,517)	(163,021)	(164,593)	(164,891)	(163,674)
Accumulated other comprehensive income		10,619	9,846	13,138	10,630	12,554	16,993	11,595
Total stockholders’ equity		126,147	119,122	118,945	103,331	103,283	105,223	100,258
Total liabilities and stockholders’ equity		176,234	169,869	173,050	156,936	154,189	156,014	146,168
Restatement Adjustment [Member]
Current assets:
Cash and cash equivalents		0	0	0	0	0	0	0	0
Accounts Receivable, Net, Current		(14,172)	(14,180)	(10,624)	(8,158)	(1,831)	(3,590)	(6,087)
Inventories		11,872	10,822	8,574	6,002	1,697	2,119	3,552
Prepaid expenses and other current assets		105	103	78	(34)	13	16	26
Total current assets		(2,195)	(3,255)	(1,972)	(2,190)	(121)	(1,455)	(2,509)
Property and equipment, net		0	0	0	0	0	0	0
Intangible assets, net		0	0	0	0	0		0
Goodwill		0	0	0	0	0	0	0
Pension asset		0	0	0	0	0	0	0
Other non-current assets		0	0	0	0	0	0	0
Total assets		(2,195)	(3,255)	(1,972)	(2,190)	(121)	(1,455)	(2,509)
Current liabilities:
Accounts payable and accrued liabilities		(36)	40	15	(3)	1,109	46	9
Accrued warranty		0	0	0	0	0	0	0
Accrued employee compensation		0	0	0	100	0	0	0
Deferred revenue		4,385	3,074	1,756	0	0	0	0
Short-term borrowings and current portion of long-term debt		0	0	0	0	0	0	0
Deferred tax liability		0	0	0	0	0	0	0
Total current liabilities		4,349	3,114	1,771	97	1,109	46	9
Deferred tax liability, long-term		0	0	0	0	0	0	0
Long-term debt, excluding current portion		0	0	0	0	0	0	0
Other long-term liabilities		0	0	0	0	0	0	0
Total liabilities		4,349	3,114	1,771	97	1,109	46	9
Commitments and contingencies (Note 12 and Note 14)
Stockholders’ equity:
Common stock, $0.10 par value per share, 40,000 shares authorized; 29,162 and 28,174 shares issued and outstanding at December 31, 2012 and 2011, respectively		0	0	0	0	0	0	0
Additional paid-in capital		0	0	0	0	0	0	0
Accumulated deficit		(6,544)	(6,369)	(3,743)	(2,287)	(1,230)	(1,501)	(2,518)
Accumulated other comprehensive income		0	0	0	0	0	0	0
Total stockholders’ equity		(6,544)	(6,369)	(3,743)	(2,287)	(1,230)	(1,501)	(2,518)
Total liabilities and stockholders’ equity		(2,195)	(3,255)	(1,972)	(2,190)	(121)	(1,455)	(2,509)
Debt Classification Adjustments [Member]
Current assets:
Cash and cash equivalents		0	0	0	0
Accounts Receivable, Net, Current		0	0	0	0
Inventories		0	0	0	0
Prepaid expenses and other current assets		41	56	59	61
Total current assets		41	56	59	61
Property and equipment, net		0	0	0	0
Intangible assets, net		0	0	0	0
Goodwill		0	0	0	0
Pension asset		0	0	0	0
Other non-current assets		(41)	(56)	(59)	(61)
Total assets		0	0	0	0
Current liabilities:
Accounts payable and accrued liabilities		0	0	0	0
Accrued warranty		0	0	0	0
Accrued employee compensation		0	0	0	0
Deferred revenue		0	0	0		2,478	1,176	419
Short-term borrowings and current portion of long-term debt		2,935	3,354	3,494	0
Deferred tax liability		0	0	0	0
Total current liabilities		2,935	3,354	3,494	0
Deferred tax liability, long-term		0	0	0	0
Long-term debt, excluding current portion		(2,935)	(3,354)	(3,494)	0
Other long-term liabilities		0	0	0	0
Total liabilities		0	0	0	0
Commitments and contingencies (Note 12 and Note 14)
Stockholders’ equity:
Common stock, $0.10 par value per share, 40,000 shares authorized; 29,162 and 28,174 shares issued and outstanding at December 31, 2012 and 2011, respectively		0	0	0	0
Additional paid-in capital		0	0	0	0
Accumulated deficit		0	0	0	0
Accumulated other comprehensive income		0	0	0	0
Total stockholders’ equity		0	0	0	0
Total liabilities and stockholders’ equity		$ 0	$ 0	$ 0	$ 0