Condensed Consolidated Statements Of Operations (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Condensed Consolidated Statements Of Operations [Abstract]        
Net sales $ 1,795 $ 1,543 $ 3,437 $ 3,060
Cost of goods sold 787 658 1,493 1,283
Gross profit 1,008 885 1,944 1,777
Operating expenses:        
Selling and marketing 383 349 793 695
General and administrative 248 226 525 479
Research and development 101 118 228 219
Total operating expenses 732 693 1,546 1,393
Operating income 276 192 398 384
Non-operating income:        
Interest income 3 1 4 4
Gain on investment securities 0 1 0 1
Other income 3 1 6 3
Total non-operating income 6 3 10 8
Income from continuing operations before income taxes 282 195 408 392
Income taxes 99 78 147 147
Income before discontinued operations 183 117 261 245
Income (loss) from discontinued operations, net of income taxes 0 1 0 (33)
Net income 183 118 261 212
Other comprehensive income (loss):        
Change in unrealized value of investments, net of income tax (508) (80) (115) 561
Total comprehensive income (loss) $ (325) $ 38 $ 146 $ 773
Net income (loss) per share data:        
Net income per share continuing operations $ 0.05 $ 0.03 $ 0.07 $ 0.07
Net loss per share discontinued operations $ 0.00 $ 0.00 $ 0.00 $ (0.01)
Net income per share $ 0.05 $ 0.03 $ 0.07 $ 0.06
Weighted average shares 3,390,785 3,388,241 3,390,752 3,386,016
Diluted        
Net income per share continuing operations $ 0.05 $ 0.03 $ 0.07 $ 0.07
Net loss per share discontinued operations $ 0.00 $ 0.00 $ 0.00 $ (0.01)
Net income per share $ 0.05 $ 0.03 $ 0.07 $ 0.06
Weighted average shares 3,407,765 3,405,468 3,407,732 3,405,358
Dividends paid per share $ 0.04 $ 0.04 $ 0.08 $ 0.08