ADJUSTED QUARTERLY FINANCIAL INFORMATION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended					9 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net sales	$ 181,394				$ 172,665	$ 509,962	$ 524,885
Cost of sales	113,610				107,686	316,785	327,655
Earnings before income taxes	18,943				21,809	55,632	56,204
Income tax expense	4,034				3,122	12,501	8,931
Net earnings	$ 14,909				$ 18,687	$ 43,131	$ 123,286
Diluted earnings (loss) per share:
Diluted - Net earnings	$ 0.57				$ 0.72	$ 1.65	$ 4.72
Contract assets	$ 94,768			$ 94,302		$ 94,768
Inventories	141,113			135,296		141,113
Total current assets	470,865			443,293		470,865
Total assets	1,408,683			1,370,186		1,408,683
Retained earnings	812,709			775,829		812,709
Total shareholders' equity	1,004,854			959,026	$ 943,457	1,004,854	$ 943,457
Total liabilities and shareholders' equity	$ 1,408,683			1,370,186		$ 1,408,683
As Reported
Net sales		$ 166,644	$ 162,949	208,030
Cost of sales		103,113	98,777	129,763
Earnings before income taxes		21,339	17,660	(16,461)
Income tax expense		5,025	3,974	5,347
Net earnings		$ 16,314	$ 13,686	$ (21,808)
Diluted earnings (loss) per share:
Diluted - Net earnings		$ 0.62	$ 0.52	$ (0.83)
Contract assets		$ 95,002	$ 93,762	$ 96,746
Inventories		145,342	144,054	136,189
Total current assets				446,630
Total assets				1,373,523
Retained earnings		804,231	790,000
Total shareholders' equity				961,595
Total liabilities and shareholders' equity				1,373,523
AS Adjusted
Net sales		165,894	162,674	205,586
Cost of sales		103,553	99,622	130,656
Earnings before income taxes		20,149	16,540	(19,798)
Income tax expense		4,745	3,722	4,579
Net earnings		$ 15,404	$ 12,818	$ (24,377)
Diluted earnings (loss) per share:
Diluted - Net earnings		$ 0.59	$ 0.49	$ (0.93)
Contract assets		$ 91,533	$ 91,043	$ 94,302
Inventories		143,164	142,316	135,296
Total current assets				443,293
Total assets				1,370,186
Retained earnings		$ 799,884	$ 786,563
Total shareholders' equity				959,026
Total liabilities and shareholders' equity				$ 1,370,186