DISCONTINUED OPERATIONS - Income statement information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue	$ 271,060	$ 340,976	$ 335,041
Income from discontinued operations before tax	8,897	14,052	14,905
Defense Electronics | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue	271,060	340,976	335,041
Cost of goods and services	232,075	285,022	269,890
Gross profit	38,985	55,954	65,151
Selling, general and administrative expenses	35,532	42,314	39,194
Income from discontinued operations	3,453	13,640	25,957
Gain on sale of business	5,291	0	0
Interest income, net	117	4	253
Other, net	36	408	(255)
Total other income (expense)	5,444	412	(2)
Income from discontinued operations before tax	$ 8,897	$ 14,052	$ 25,955