REVENUE - Contract Balances (Details) - USD ($)	9 Months Ended
	Jun. 30, 2020	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Contract costs and recognized income not yet billed, net of progress payments	$ 92,143,000	$ 105,111,000
Decrease in contract assets balance	12,968,000
Contract costs and recognized income not yet billed, noncurrent	7,058,000	13,100,000
Reserves for contract risk	1,874,000	0
Contract liabilities	20,719,000	$ 26,259,000
Increase (decrease) in contract liabilities	$ (5,540,000)