REVENUE - Cumulative Effective of Adoption of ASC 606 (Details) $ in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 CAD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 CAD ($)	Sep. 30, 2017 USD ($)	Oct. 01, 2018 USD ($)	Sep. 30, 2016 USD ($)
CURRENT ASSETS
Contract costs and recognized income not yet billed, net of progress payments	$ 105,111				$ 121,803				$ 105,111		$ 121,803			$ 100,821
Inventories	442,121				398,359				442,121		398,359			420,384
Total Current Assets	925,179				912,874				925,179		912,874			913,917
Assets	2,074,939				2,084,890				2,074,939		2,084,890		$ 1,873,541	2,085,933
CURRENT LIABILITIES
Accounts payable	250,576				233,658				250,576		233,658			241,940
Billings in excess of costs	26,259								26,259					25,841
Total Current Liabilities	390,099				393,071				390,099		393,071			401,353
OTHER LIABILITIES	109,997				106,710				109,997		106,710			105,089
Liabilities	1,597,176				1,610,499				1,597,176		1,610,499			1,617,160
SHAREHOLDERS’ EQUITY
Retained earnings	568,516				550,523				568,516		550,523			544,905
Total Shareholders' Equity	477,763				474,391				477,763		474,391		398,808	468,773	$ 410,947
Total Liabilities and Shareholders’ Equity	2,074,939				2,084,890				2,074,939		2,084,890			2,085,933
Income Statement
Net sales									2,209,289	$ 3,500	1,977,918	$ 700	1,524,997
Cost of goods and services									1,614,020		1,448,737		1,116,871
Income (loss) before taxes from continuing operations									72,178		33,810		16,698
Provision (benefit) from income taxes									26,556		555		(1,085)
Income (loss) from continuing operations	16,251	$ 14,128	$ 6,490	$ 8,753	1,031	$ 7,442	$ 1,951	$ 22,831	45,622		33,255		$ 17,783
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
CURRENT ASSETS
Contract costs and recognized income not yet billed, net of progress payments	119,348				121,803				119,348		121,803
Inventories	424,309				398,359				424,309		398,359
Total Current Assets	921,604				912,874				921,604		912,874
Assets	2,071,364				2,084,890				2,071,364		2,084,890
CURRENT LIABILITIES
Accounts payable	242,294				233,658				242,294		233,658
Billings in excess of costs	17,977				17,559				17,977		17,559
Total Current Liabilities	381,817				393,071				381,817		393,071
OTHER LIABILITIES	111,066				106,710				111,066		106,710
Liabilities	1,589,963				1,610,499				1,589,963		1,610,499
SHAREHOLDERS’ EQUITY
Retained earnings	572,154				550,523				572,154		550,523
Total Shareholders' Equity	481,401				474,391				481,401		474,391
Total Liabilities and Shareholders’ Equity	2,071,364				$ 2,084,890				2,071,364		$ 2,084,890
Income Statement
Net sales									2,202,544
Cost of goods and services									1,609,807
Income (loss) before taxes from continuing operations									69,646
Provision (benefit) from income taxes									26,004
Income (loss) from continuing operations									43,642
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
CURRENT ASSETS
Contract costs and recognized income not yet billed, net of progress payments	(14,237)								(14,237)					(20,982)
Inventories	17,812								17,812					22,025
Total Current Assets	3,575								3,575					1,043
Assets	3,575								3,575					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	(1,069)								(1,069)					(1,621)
Liabilities	7,213								7,213					6,661
SHAREHOLDERS’ EQUITY
Retained earnings	(3,638)								(3,638)					(5,618)
Total Shareholders' Equity	(3,638)								(3,638)					(5,618)
Total Liabilities and Shareholders’ Equity	$ 3,575								3,575					$ 1,043
Income Statement
Net sales									6,745
Cost of goods and services									4,213
Income (loss) before taxes from continuing operations									2,532
Provision (benefit) from income taxes									552
Income (loss) from continuing operations									$ 1,980