Consolidated Condensed Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock at $1 par value	[1]	Capital in excess of par value	Reinvested earnings	Accumulated other comprehensive income (loss)	Employee benefit stock	Treasury stock (at cost)
Balance at beginning of period at Dec. 31, 2017	$ 277,451	$ 37,165		$ 32,182	$ 244,224	$ (10,893)	$ (461)	$ (24,766)
Increase (Decrease) in Stockholders' Equity
Net earnings	16,551				16,551
ASU adoption impact | Accounting Standards Update 2014-09	(128)				(128)
ASU adoption impact | Accounting Standards Update 2018-02	(1,700)				1,700	(1,700)
Pension and postretirement benefits (net of tax effect)	13,168					13,168
Foreign currency translation	(281)					(281)
Cash dividends	(11,915)				(11,915)
Stock options exercised	933	33		900
Stock-based compensation	3,374			3,374
Purchase of common stock for treasury stock	(4,451)							(4,451)
Issuance of treasury stock	528			353				175
Balance at end of period at Sep. 30, 2018	295,230	37,198		36,809	250,432	294	(461)	(29,042)
Balance at beginning of period at Jun. 30, 2018	288,470	37,177		33,681	250,242	(5,508)	(461)	(26,661)
Increase (Decrease) in Stockholders' Equity
Net earnings	2,851				2,851
ASU adoption impact | Accounting Standards Update 2018-02					1,700	(1,700)
Pension and postretirement benefits (net of tax effect)	7,396					7,396
Foreign currency translation	106					106
Cash dividends	(4,361)				(4,361)
Stock options exercised	702	21		681
Stock-based compensation	2,430			2,430
Purchase of common stock for treasury stock	(2,462)							(2,462)
Issuance of treasury stock	98			17				81
Balance at end of period at Sep. 30, 2018	295,230	37,198		36,809	250,432	294	(461)	(29,042)
Balance at beginning of period at Dec. 31, 2018	303,503	37,198		38,082	257,313	580	(306)	(29,364)
Increase (Decrease) in Stockholders' Equity
Net earnings	34,903				34,903
Pension and postretirement benefits (net of tax effect)	333					333
Foreign currency translation	(509)					(509)
Cash dividends	(13,665)				(13,665)
Stock options exercised	963	2		832				129
Stock-based compensation	882			882
Purchase of common stock for treasury stock	(3,358)							(3,358)
Issuance of treasury stock	587			510				77
Balance at end of period at Sep. 30, 2019	323,639	37,200		40,306	278,551	404	(306)	(32,516)
Balance at beginning of period at Jun. 30, 2019	316,452	37,200		39,746	270,772	1,066	(306)	(32,026)
Increase (Decrease) in Stockholders' Equity
Net earnings	12,721				12,721
Pension and postretirement benefits (net of tax effect)	(16)					(16)
Foreign currency translation	(646)					(646)
Cash dividends	(4,942)				(4,942)
Stock options exercised	215			192				23
Stock-based compensation	328			328
Purchase of common stock for treasury stock	(521)							(521)
Issuance of treasury stock	48			40				8
Balance at end of period at Sep. 30, 2019	$ 323,639	$ 37,200		$ 40,306	$ 278,551	$ 404	$ (306)	$ (32,516)

[1] Each common share of stock equals $1 par value; therefore, the number of common shares is the same as the dollar value.