Condensed Consolidated Statements Of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock Outstanding [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Balance (in shares) at Jun. 30, 2022		27,520,000
Balance at Jun. 30, 2022	$ 844,687	$ 137,814	$ 1,485,045	$ (11,172)	$ (767,000)
Net income	37,592		37,592
Net pension and postretirement benefit gains, net of tax effect	95			95
Cash dividends - common stock	(22,067)		(22,067)
Purchase of treasury stock (in shares)		0
Purchase of treasury stock	(84)				(84)
Stock-based plans (in shares)		34,000
Stock-based plans	(617)	$ (617)
Stock-based compensation expense	2,465	$ 2,465
Balance (in shares) at Sep. 30, 2022		27,554,000
Balance at Sep. 30, 2022	862,071	$ 139,662	1,500,570	(11,077)	(767,084)
Balance (in shares) at Jun. 30, 2022		27,520,000
Balance at Jun. 30, 2022	844,687	$ 137,814	1,485,045	(11,172)	(767,000)
Net income	77,565
Net pension and postretirement benefit gains, net of tax effect	190
Balance (in shares) at Dec. 31, 2022		27,571,000
Balance at Dec. 31, 2022	879,550	$ 140,660	1,517,081	(10,982)	(767,209)
Balance (in shares) at Sep. 30, 2022		27,554,000
Balance at Sep. 30, 2022	862,071	$ 139,662	1,500,570	(11,077)	(767,084)
Net income	39,973		39,973
Net pension and postretirement benefit gains, net of tax effect	95			95
Cash dividends - common stock	(23,462)		(23,462)
Purchase of treasury stock (in shares)		(1,000)
Purchase of treasury stock	(125)				(125)
Stock-based plans (in shares)		18,000
Stock-based plans	(1,801)	$ (1,801)
Stock-based compensation expense	2,799	$ 2,799
Balance (in shares) at Dec. 31, 2022		27,571,000
Balance at Dec. 31, 2022	$ 879,550	$ 140,660	1,517,081	(10,982)	(767,209)
Balance (in shares) at Jun. 30, 2023	27,527,550	27,528,000
Balance at Jun. 30, 2023	$ 862,267	$ 143,870	1,503,963	(9,365)	(776,201)
Net income	43,951		43,951
Net pension and postretirement benefit gains, net of tax effect	76			76
Cash dividends - common stock	(23,445)		(23,445)
Purchase of treasury stock (in shares)		(40,000)
Purchase of treasury stock	(6,650)				(6,650)
Stock-based plans (in shares)		29,000
Stock-based plans	0	$ 0
Stock-based compensation expense	2,569	$ 2,569
Balance (in shares) at Sep. 30, 2023		27,517,000
Balance at Sep. 30, 2023	$ 878,768	$ 146,439	1,524,469	(9,289)	(782,851)
Balance (in shares) at Jun. 30, 2023	27,527,550	27,528,000
Balance at Jun. 30, 2023	$ 862,267	$ 143,870	1,503,963	(9,365)	(776,201)
Net income	95,435
Net pension and postretirement benefit gains, net of tax effect	$ 151
Balance (in shares) at Dec. 31, 2023	27,521,158	27,521,000
Balance at Dec. 31, 2023	$ 908,326	$ 149,290	1,551,143	(9,214)	(782,893)
Balance (in shares) at Sep. 30, 2023		27,517,000
Balance at Sep. 30, 2023	878,768	$ 146,439	1,524,469	(9,289)	(782,851)
Net income	51,484		51,484
Net pension and postretirement benefit gains, net of tax effect	75			75
Cash dividends - common stock	(24,810)		(24,810)
Purchase of treasury stock (in shares)		0
Purchase of treasury stock	(42)				(42)
Stock-based plans (in shares)		4,000
Stock-based plans	(3)	$ (3)
Stock-based compensation expense	$ 2,854	$ 2,854
Balance (in shares) at Dec. 31, 2023	27,521,158	27,521,000
Balance at Dec. 31, 2023	$ 908,326	$ 149,290	$ 1,551,143	$ (9,214)	$ (782,893)