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, 2019		27,491,000
Balance at Jun. 30, 2019	$ 726,873	$ 122,844	$ 1,359,782	$ (10,308)	$ (745,445)
Net income	40,745		40,745
Net pension and postretirement benefit gains, net of tax effect	70			70
Cash dividends - common stock	(17,869)		(17,869)
Purchase of treasury stock (in shares)		(10,000)
Purchase of treasury stock	(1,465)				(1,465)
Stock-based plans (in shares)		4,000
Stock-based plans	(125)	$ (125)
Stock-based compensation expense	1,436	$ 1,436
Balance (in shares) at Sep. 30, 2019		27,485,000
Balance at Sep. 30, 2019	$ 749,665	$ 124,155	1,382,658	(10,238)	(746,910)
Balance (in shares) at Jun. 30, 2020	27,523,935	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	27,539,988	27,540,000
Balance at Sep. 30, 2020	$ 801,106	$ 125,071	$ 1,438,930	$ (11,976)	$ (750,919)