DISCONTINUED OPERATIONS - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended	24 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) position
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue from disposed business	$ 53,993	$ 67,768
Restructuring charges	1,716	3,079
Liabilities of discontinued operations held-for-sale	6,835		$ 7,074	$ 7,074
Discontinued Operations | Installation Services and Other Discontinued Activities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue from disposed business	0	0
Discontinued Operations | Defense Electronics
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consulting and stay bonuses cost	1,792
Pro forma depreciation and amortization from Defense Electronics	$ 2,700
Discontinued Operations | Defense Electronics | Voluntary Employee Retirement Plan and Reduction In Force
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring charges		2,200
Reduction of headcount | position				90
Discontinued Operations | Defense Electronics | Exit of Older Weather Radar Product Lines
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business exit costs			$ 5,601
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations | Systems Engineering Group, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue from disposed business		$ 6,713