Statements of Consolidated Income - USD ($)
shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Income Statement [Abstract]      
Net sales $ 336,634 $ 354,666 $ 388,185
Cost of products sold 227,220 251,214 267,237
GROSS PROFIT 109,414 103,452 120,948
Costs and expenses      
Selling 31,799 30,593 35,655
General and administrative 42,057 36,878 42,563
Research and engineering 14,025 14,879 16,302
Other operating expenses - net 54 8,753 5,190
Total costs and expenses 87,935 91,103 99,710
OPERATING INCOME 21,479 12,349 21,238
Other income (expense)      
Interest income 291 391 483
Interest expense (844) (565) (658)
Other income (expense) 27 (469) 347
Total other income (expense) (526) (643) 172
INCOME BEFORE INCOME TAXES 20,953 11,706 21,410
Income taxes 5,698 5,031 8,549
NET INCOME $ 15,255 $ 6,675 $ 12,861
BASIC EARNINGS PER SHARE      
Net income $ 2.95 $ 1.25 $ 2.39
DILUTED EARNINGS PER SHARE      
Net income 2.95 1.24 2.39
Cash dividends declared per share $ 0.80 $ 0.80 $ 0.80
Weighted-average number of shares outstanding - basic 5,166 5,350 5,377
Weighted-average number of shares outstanding - diluted 5,178 5,366 5,382