REVENUE - Cumulative Effective of Adoption of ASC 606 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Oct. 01, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
CURRENT ASSETS
Contract costs and recognized income not yet billed, net of progress payments	$ 83,904		$ 83,904			$ 100,821	$ 121,803
Inventories	457,071		457,071			420,384	398,359
Total Current Assets	989,105		989,105			913,917	912,874
Total Assets	2,143,908		2,143,908			2,085,933	2,084,890
CURRENT LIABILITIES
Accounts payable	223,188		223,188			241,940	233,658
Billings in excess of costs	28,227		28,227			25,841
Total Current Liabilities	366,184		366,184			401,353	393,071
OTHER LIABILITIES	94,938		94,938			105,144	106,710
Total Liabilities	1,669,624		1,669,624			1,617,215	1,610,499
SHAREHOLDERS’ EQUITY
Retained Earnings	545,600		545,600			544,850
Total Shareholders' Equity	474,284	$ 474,018	474,284	$ 474,018	$ 471,561	468,718	474,391	$ 434,813	$ 398,808
Total Liabilities and Shareholders’ Equity	2,143,908		2,143,908			2,085,933	2,084,890
Income Statement
Net sales	549,633	478,560	1,060,155	915,863
Cost of goods and services	412,129	357,181	779,605	673,705
Income (loss) before taxes from continuing operations	9,684	3,188	23,649	1,115
Provision (benefit) from income taxes	3,194	1,237	8,406	(23,667)
Income from continuing operations	6,490	$ 1,951	15,243	$ 24,782
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
CURRENT ASSETS
Contract costs and recognized income not yet billed, net of progress payments	98,700		98,700				121,803
Inventories	439,543		439,543				398,359
Total Current Assets	986,373		986,373				912,874
Total Assets	2,141,176		2,141,176				2,084,890
CURRENT LIABILITIES
Accounts payable	214,906		214,906				233,658
Billings in excess of costs	19,945		19,945				17,559
Total Current Liabilities	357,902		357,902				393,071
OTHER LIABILITIES	96,136		96,136				106,710
Total Liabilities	1,662,540		1,662,540				1,610,499
SHAREHOLDERS’ EQUITY
Retained Earnings	549,952		549,952				550,523
Total Shareholders' Equity	478,636		478,636				474,391
Total Liabilities and Shareholders’ Equity	2,141,176		2,141,176				$ 2,084,890
Income Statement
Net sales	548,053		1,053,969
Cost of goods and services	410,898		775,109
Income (loss) before taxes from continuing operations	9,335		21,960
Provision (benefit) from income taxes	3,118		8,038
Income from continuing operations	6,217		13,922
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 (ASC 606) [Member]
CURRENT ASSETS
Contract costs and recognized income not yet billed, net of progress payments	(14,796)		(14,796)			(20,982)
Inventories	17,528		17,528			22,025
Total Current Assets	2,732		2,732			1,043
Total Assets	2,732		2,732			1,043
CURRENT LIABILITIES
Accounts payable	8,282		8,282			8,282
Billings in excess of costs	8,282		8,282			8,282
Total Current Liabilities	8,282		8,282			8,282
OTHER LIABILITIES	(1,198)		(1,198)			(1,566)
Total Liabilities	7,084		7,084			6,716
SHAREHOLDERS’ EQUITY
Retained Earnings	(4,352)		(4,352)			(5,673)
Total Shareholders' Equity	(4,352)		(4,352)			(5,673)
Total Liabilities and Shareholders’ Equity	2,732		2,732			$ 1,043
Income Statement
Net sales	1,580		6,186
Cost of goods and services	1,231		4,496
Income (loss) before taxes from continuing operations	349		1,689
Provision (benefit) from income taxes	76		368
Income from continuing operations	$ 273		$ 1,321