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, 2020		27,524,000
Balance at Jun. 30, 2020	$ 783,300	$ 125,153	$ 1,421,121	$ (12,070)	$ (750,904)
Net income	37,079		37,079
Net pension and postretirement benefit gains, net of tax effect	94			94
Cash dividends - common stock	(19,270)		(19,270)
Purchase of treasury stock (in shares)		0
Purchase of treasury stock	(15)				(15)
Stock-based plans (in shares)		16,000
Stock-based plans	(1,854)	$ (1,854)
Stock-based compensation expense	1,772	$ 1,772
Balance (in shares) at Sep. 30, 2020		27,540,000
Balance at Sep. 30, 2020	801,106	$ 125,071	1,438,930	(11,976)	(750,919)
Balance (in shares) at Jun. 30, 2020		27,524,000
Balance at Jun. 30, 2020	783,300	$ 125,153	1,421,121	(12,070)	(750,904)
Net income	81,709
Net pension and postretirement benefit gains, net of tax effect	188
Balance (in shares) at Dec. 31, 2020		27,547,000
Balance at Dec. 31, 2020	826,360	$ 126,260	1,462,905	(11,882)	(750,923)
Balance (in shares) at Sep. 30, 2020		27,540,000
Balance at Sep. 30, 2020	801,106	$ 125,071	1,438,930	(11,976)	(750,919)
Net income	44,630		44,630
Net pension and postretirement benefit gains, net of tax effect	94			94
Cash dividends - common stock	(20,655)		(20,655)
Purchase of treasury stock (in shares)		0
Purchase of treasury stock	(4)				(4)
Stock-based plans (in shares)		7,000
Stock-based plans	(581)	$ (581)
Stock-based compensation expense	1,770	$ 1,770
Balance (in shares) at Dec. 31, 2020		27,547,000
Balance at Dec. 31, 2020	$ 826,360	$ 126,260	1,462,905	(11,882)	(750,923)
Balance (in shares) at Jun. 30, 2021	27,531,040	27,531,000
Balance at Jun. 30, 2021	$ 843,147	$ 128,617	1,482,220	(8,253)	(759,437)
Net income	30,655		30,655
Net pension and postretirement benefit gains, net of tax effect	42			42
Cash dividends - common stock	(20,675)		(20,675)
Purchase of treasury stock (in shares)		(30,000)
Purchase of treasury stock	(5,329)				(5,329)
Stock-based plans (in shares)		29,000
Stock-based plans	(59)	$ (59)
Stock-based compensation expense	2,274	$ 2,274
Balance (in shares) at Sep. 30, 2021		27,530,000
Balance at Sep. 30, 2021	$ 850,055	$ 130,832	1,492,200	(8,211)	(764,766)
Balance (in shares) at Jun. 30, 2021	27,531,040	27,531,000
Balance at Jun. 30, 2021	$ 843,147	$ 128,617	1,482,220	(8,253)	(759,437)
Net income	65,025
Net pension and postretirement benefit gains, net of tax effect	$ 83
Balance (in shares) at Dec. 31, 2021	27,533,957	27,534,000
Balance at Dec. 31, 2021	$ 865,009	$ 133,419	1,504,535	(8,170)	(764,775)
Balance (in shares) at Sep. 30, 2021		27,530,000
Balance at Sep. 30, 2021	850,055	$ 130,832	1,492,200	(8,211)	(764,766)
Net income	34,370		34,370
Net pension and postretirement benefit gains, net of tax effect	41			41
Cash dividends - common stock	(22,035)		(22,035)
Purchase of treasury stock (in shares)		0
Purchase of treasury stock	(9)				(9)
Stock-based plans (in shares)		4,000
Stock-based plans	(2)	$ (2)
Stock-based compensation expense	$ 2,589	$ 2,589
Balance (in shares) at Dec. 31, 2021	27,533,957	27,534,000
Balance at Dec. 31, 2021	$ 865,009	$ 133,419	$ 1,504,535	$ (8,170)	$ (764,775)