Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock at $1 par value		Capital in excess of par value	Reinvested earnings	Accumulated other comprehensive income (loss)	Employee benefit stock	Treasury stock
Balance at beginning of period at Dec. 31, 2014	$ 214,331	$ 41,046	[1]	$ 27,830	$ 189,365	$ (11,856)	$ (922)	$ (31,132)
Increase (Decrease) in Stockholders' Equity
Net earnings	25,938				25,938
Pension and postretirement benefits (net of tax effect)	(77)					(77)
Foreign currency translation	(847)					(847)
Cash dividends	(11,259)				(11,259)
Stock options exercised	1,641	57	[1]	1,517				67
Tax benefit on stock options and dividends	141			141
ESSOP transactions	396			242			154
Stock-based compensation	1,541			1,541
Issuance of treasury stock	470			355				115
Balance at end of period at Dec. 31, 2015	232,275	41,103	[1]	31,626	204,044	(12,780)	(768)	(30,950)
Increase (Decrease) in Stockholders' Equity
Net earnings	32,295				32,295
Pension and postretirement benefits (net of tax effect)	1,473					1,473
Foreign currency translation	(328)					(328)
Cash dividends	(12,463)				(12,463)
Stock options exercised	569	19	[1]	528				22
Tax benefit on stock options and dividends	(110)			(110)
ESSOP transactions	443			289			154
Stock-based compensation	1,537			1,537
Retirement of treasury stock	0	(4,000)		(6,260)				10,260
Issuance of treasury stock	518			412				106
Balance at end of period at Dec. 31, 2016	256,209	37,122	[1]	28,022	223,876	(11,635)	(614)	(20,562)
Increase (Decrease) in Stockholders' Equity
Net earnings	34,571				34,571
Pension and postretirement benefits (net of tax effect)	(1,102)					(1,102)
Foreign currency translation	1,844					1,844
Cash dividends	(14,223)				(14,223)
Stock options exercised	1,871	43	[1]	1,798				30
ESSOP transactions	359			205			154
Stock-based compensation	1,725			1,725
Purchase of common stock for treasury stock	(4,402)							(4,402)
Issuance of treasury stock	600			432				168
Balance at end of period at Dec. 31, 2017	$ 277,452	$ 37,165	[1]	$ 32,182	$ 244,224	$ (10,893)	$ (460)	$ (24,766)

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