Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares	Common Shares Held In Treasury	Common Stock	Retained Earnings	Common Stock In Treasury	Accumulated Other Comprehensive Income (Loss)	Other Equity Transactions
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares		19,949
Common shares held in Treasury			7,200
Beginning balances at Dec. 31, 2016	$ 494,089			$ 212,702	$ 517,903	$ (154,399)	$ (86,181)	$ 4,064
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,451			0	11,451	0	0	0
Other comprehensive income (loss), net of tax	(2,081)			0	0	0	(2,081)	0
Net pension curtailments and settlements	0
Tax Cuts and Jobs Act Reclassification	0			0	14,675	0	(14,675)	0
Cash dividends declared	(7,913)			0	(7,913)	0	0	0
Stock-based compensation activity, in shares		296	(296)
Stock-based compensation activity	4,956			10,750	0	(5,794)	0	0
Payments for withholding taxes for stock-based compensation awards, in shares		(108)	108
Payments of withholding taxes for stock-based compensation awards	(4,506)			0	0	(4,506)	0	0
Repurchase of shares		32	32
Repurchase of 32, 10, and 5 shares for the years ended 2017, 2018, and 2019, respectively	(1,086)			0	0	(1,086)	0	0
Directors' deferred compensation, in shares		2	(2)
Directors' deferred compensation	71			32	0	(343)	0	382
Ending balances at Dec. 31, 2017	494,981			223,484	536,116	(166,128)	(102,937)	4,446
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares		20,107
Common shares held in Treasury			7,042
Net income	20,846			0	20,846	0	0	0
Other comprehensive income (loss), net of tax	2,722			0	0	0	2,722	0
Net pension curtailments and settlements	41,406			0	0	0	41,406	0
Pension settlement charges	41,400
Tax Cuts and Jobs Act Reclassification	0			0	(575)	0	575	0
Cumulative effect of accounting change	425			0	425	0	0	0
Cash dividends declared	(8,389)			0	(8,389)	0	0	0
Stock-based compensation activity, in shares		202	(203)
Stock-based compensation activity	5,314			11,131	(49)	(5,768)	0	0
Payments for withholding taxes for stock-based compensation awards, in shares		(60)	60
Payments of withholding taxes for stock-based compensation awards	(3,156)			0	0	(3,156)	0	0
Repurchase of shares		10	10
Repurchase of 32, 10, and 5 shares for the years ended 2017, 2018, and 2019, respectively	(422)			0	0	(422)	0	0
Directors' deferred compensation, in shares		3	(3)
Directors' deferred compensation	179			89	0	48	0	42
Ending balances at Dec. 31, 2018	$ 553,906			234,704	548,374	(175,426)	(58,234)	4,488
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares		20,242
Common shares held in Treasury	6,906		6,906
Net income	$ 50,660			0	50,660	0	0	0
Other comprehensive income (loss), net of tax	9,444			0	0	0	9,444	0
Net pension curtailments and settlements	3,328
Pension settlement charges	3,328			0	0	0	3,328	0
Cumulative effect of accounting change	(179)			0	(179)	0	0	0
Cash dividends declared	(8,856)			0	(8,856)	0	0	0
Stock-based compensation activity, in shares		252	(252)
Stock-based compensation activity	7,170			14,876	(111)	(7,595)	0	0
Payments for withholding taxes for stock-based compensation awards, in shares		(89)	89
Payments of withholding taxes for stock-based compensation awards	(4,846)			0	0	(4,846)	0	0
Repurchase of shares		5	5
Repurchase of 32, 10, and 5 shares for the years ended 2017, 2018, and 2019, respectively	(199)			0	0	(199)	0	0
Directors' deferred compensation, in shares		4	(4)
Directors' deferred compensation	249			94	0	1,221	0	(1,066)
Ending balances at Dec. 31, 2019	$ 610,677			$ 249,674	$ 589,888	$ (186,845)	$ (45,462)	$ 3,422
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares		20,404
Common shares held in Treasury	6,744		6,744