CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-In Capital [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive income (loss) [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive income (loss) [Member]	Treasury Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Total
Beginning Balance at Sep. 30, 2017		$ 305		$ 289,785		$ 516,718		$ (27,308)		$ (107,582)		$ 671,918
Balance (in shares) at Sep. 30, 2017		30,469
Comprehensive income (loss):
Net earnings		$ 0		0		92,136		0		0		92,136
Translation adjustments, net of tax		0		0		0		(2,254)		0		(2,254)
Amortization of prior service costs and actuarial losses		0		0		0		(2,003)		0		(2,003)
Forward exchange contracts, net of tax		0		0		0		37		0		37
Cash dividends declared		0		0		(8,278)		0		0		(8,278)
Reclassification from accumulated other comprehensive loss as a result of the adoption of new accounting standard ASU 2018-02						(6,261)		0		0		(6,261)
Stock options and stock compensation plans, net of tax		$ 0		1,405		0		0		188		1,593
Stock options and stock compensation plans, net of tax (in shares)		66
Ending Balance at Sep. 30, 2018		$ 305		291,190		606,837		(31,528)		(107,394)		759,410
Ending Balance (in shares) at Sep. 30, 2018		30,535
Comprehensive income (loss):
Net earnings		$ 0		0		81,039		0		0		81,039
Translation adjustments, net of tax		0		0		0		(6,474)		0		(6,474)
Amortization of prior service costs and actuarial losses		0		0		0		(6,066)		0		(6,066)
Forward exchange contracts, net of tax		0		0		0		94		0		94
Cash dividends declared		0		0		(8,302)		0		0		(8,302)
Stock options and stock compensation plans, net of tax		$ 1		1,218		0		0		135		1,354
Stock options and stock compensation plans, net of tax (in shares)		62
Ending Balance at Sep. 30, 2019		$ 306		292,408		684,741		(43,974)		(107,259)		826,222
Ending Balance (in shares) at Sep. 30, 2019		30,597
Comprehensive income (loss):
Adoption of new accounting standard ASU 2014-09	$ 0		$ 0		$ (5,167)		$ 0		$ 0		$ (5,167)
Net earnings		$ 0		0		101,980		0		0		101,980
Translation adjustments, net of tax		0		0		0		3,172		0		3,172
Amortization of prior service costs and actuarial losses												(3,455)
Cash dividends declared		0		0		(8,323)		0		0		(8,323)
Stock options and stock compensation plans, net of tax		$ 0		1,274		0		0		125		1,399
Stock options and stock compensation plans, net of tax (in shares)		49
Pension termination and net unrecognized actuarial loss, net of tax		$ 0		0		0		(37,145)		0		(37,145)
Ending Balance at Sep. 30, 2020		$ 306		$ 293,682		$ 778,398		$ (3,657)		$ (107,134)		$ 961,595
Ending Balance (in shares) at Sep. 30, 2020		30,646