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, 2013		$ 297,780	$ 6,290	$ 1,581	$ 941	$ 301,227	$ (803)	$ 1,021	$ 676	$ (13,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		1,433	26		1,407
Purchase of treasury shares		(26,447)	(502)		(2,348)	(23,597)
Conversion of Class B to Class A shares			7	(7)
Net income	$ 2,551	2,551				2,551
Cash dividends on Class A and Class B common stock: $0.7825 per share		(5,884)	0	0		(5,884)
Current period other comprehensive income (loss)		(1,246)					(656)	270	(860)	0
Reclassification adjustment to net income (loss)		1,055							602	453
Balance, end of period at Sep. 30, 2014		269,242	5,821	1,574	0	274,297	(1,459)	1,291	418	(12,700)
Balance, beginning of period at Dec. 31, 2014		211,474	5,662	1,573	0	224,428	(2,699)	1,463	56	(19,009)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		896	40		856
Purchase of treasury shares		(23,248)	(426)		(856)	(21,966)
Conversion of Class B to Class A shares			1	(1)
Net income	$ 3,893	3,893				3,893
Cash dividends on Class A and Class B common stock: $0.7825 per share		(5,502)				(5,502)
Current period other comprehensive income (loss)		(3,773)					(2,352)	(205)	(1,216)	0
Reclassification adjustment to net income (loss)		1,004							363	641
Balance, end of period at Sep. 30, 2015		$ 184,744	$ 5,277	$ 1,572	$ 0	$ 200,853	$ (5,051)	$ 1,258	$ (797)	$ (18,368)