Unaudited Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Total Stockholders' Equity	Common Stock Shares Outstanding Class A	Common Stock Shares Outstanding Class B	Capital in Excess of Par Value	Retained Earnings	Foreign Currency Translation Adjustment	Deferred Gain (Loss) on Available for Sale Securities	Deferred Gain (Loss) on Cash Flow Hedging	Pension and Postretirement Plan Adjustment
Balance, beginning of period at Dec. 31, 2015		$ 201,138	$ 5,265	$ 1,572	$ 0	$ 217,745	$ (5,455)	$ 1,480	$ (112)	$ (19,357)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		754	42		712
Conversion of Class B to Class A shares			1	(1)
Net income	$ 2,802	2,802				2,802
Cash dividends on Class A and Class B common stock		(1,804)				(1,804)
Current period other comprehensive income (loss)		(1,095)					207	65	(1,367)
Reclassification adjustment to net income		224							75	149
Balance, end of period at Mar. 31, 2016		202,019	5,308	1,571	712	218,743	(5,248)	1,545	(1,404)	(19,208)
Balance, beginning of period at Dec. 31, 2016		220,293	5,208	1,571	0	239,441	(7,533)	1,893	393	(20,680)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		(158)	55		0	(213)
Net income	$ 4,978	4,978				4,978
Cash dividends on Class A and Class B common stock		(1,827)				(1,827)
Current period other comprehensive income (loss)		1,058					1,071	226	(239)
Reclassification adjustment to net income		182							6	176
Balance, end of period at Mar. 31, 2017		$ 224,526	$ 5,263	$ 1,571	$ 0	$ 242,379	$ (6,462)	$ 2,119	$ 160	$ (20,504)