CONSOLIDATING GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details) - Summary of Condensed Consolidating Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Oct. 01, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017
CURRENT ASSETS
Cash and equivalents	$ 57,979			$ 69,758	$ 236,456		$ 47,681
Accounts receivable, net of allowances	344,049			280,509
Contract costs and recognized income not yet billed, net of progress payments	83,904		$ 100,821	121,803
Inventories	457,071		420,384	398,359
Prepaid and other current assets	45,778			42,121
Assets of discontinued operations	324			324
Total Current Assets	989,105		913,917	912,874
PROPERTY, PLANT AND EQUIPMENT, net	332,852			342,492
GOODWILL	439,118			439,395
INTANGIBLE ASSETS, net	364,740			370,858
INTERCOMPANY RECEIVABLE	0			0
EQUITY INVESTMENTS IN SUBSIDIARIES	0			0
OTHER ASSETS	15,192			16,355
ASSETS OF DISCONTINUED OPERATIONS	2,901			2,916
Total Assets	2,143,908		2,085,933	2,084,890
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	10,807			13,011
Accounts payable and accrued liabilities	343,720			372,850
Liabilities of discontinued operations	11,657			7,210
Total Current Liabilities	366,184		401,353	393,071
LONG-TERM DEBT, net of debt discounts	1,206,195			1,108,071
INTERCOMPANY PAYABLES	0			0
OTHER LIABILITIES	94,938		105,144	106,710
LIABILITIES OF DISCONTINUED OPERATIONS	2,307			2,647
Total Liabilities	1,669,624		1,617,215	1,610,499
Total Shareholders’ Equity	474,284	$ 471,561	468,718	474,391	474,018	$ 434,813	398,808
Total Liabilities and Shareholders’ Equity	2,143,908		$ 2,085,933	2,084,890
Parent Company [Member]
CURRENT ASSETS
Cash and equivalents	5,067			15,976	177,429		3,240
Accounts receivable, net of allowances	0			0
Contract costs and recognized income not yet billed, net of progress payments	0			0
Inventories	0			0
Prepaid and other current assets	17,735			12,179
Assets of discontinued operations	0			0
Total Current Assets	22,802			28,155
PROPERTY, PLANT AND EQUIPMENT, net	1,005			936
GOODWILL	0			6,646
INTANGIBLE ASSETS, net	93			93
INTERCOMPANY RECEIVABLE	122,555			56,396
EQUITY INVESTMENTS IN SUBSIDIARIES	1,552,035			1,528,932
OTHER ASSETS	7,180			8,651
ASSETS OF DISCONTINUED OPERATIONS	0			0
Total Assets	1,705,670			1,629,809
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	0			2,276
Accounts payable and accrued liabilities	17,409			26,639
Liabilities of discontinued operations	0			0
Total Current Liabilities	17,409			28,915
LONG-TERM DEBT, net of debt discounts	1,146,231			1,044,071
INTERCOMPANY PAYABLES	56,415			66,058
OTHER LIABILITIES	11,331			16,374
LIABILITIES OF DISCONTINUED OPERATIONS	0			0
Total Liabilities	1,231,386			1,155,418
Total Shareholders’ Equity	474,284			474,391
Total Liabilities and Shareholders’ Equity	1,705,670			1,629,809
Guarantor Companies [Member]
CURRENT ASSETS
Cash and equivalents	31,858			16,353	22,937		8,066
Accounts receivable, net of allowances	288,362			234,885
Contract costs and recognized income not yet billed, net of progress payments	82,811			121,393
Inventories	389,223			332,067
Prepaid and other current assets	19,910			21,313
Assets of discontinued operations	0			0
Total Current Assets	812,164			726,011
PROPERTY, PLANT AND EQUIPMENT, net	291,449			299,920
GOODWILL	394,056			361,507
INTANGIBLE ASSETS, net	278,055			293,093
INTERCOMPANY RECEIVABLE	679,010			314,394
EQUITY INVESTMENTS IN SUBSIDIARIES	512,201			968,330
OTHER ASSETS	16,774			15,942
ASSETS OF DISCONTINUED OPERATIONS	0			0
Total Assets	2,983,709			2,979,197
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	3,495			3,398
Accounts payable and accrued liabilities	292,428			303,154
Liabilities of discontinued operations	0			(22,327)
Total Current Liabilities	295,923			284,225
LONG-TERM DEBT, net of debt discounts	4,378			6,110
INTERCOMPANY PAYABLES	381,703			(77,760)
OTHER LIABILITIES	69,856			73,391
LIABILITIES OF DISCONTINUED OPERATIONS	0			0
Total Liabilities	751,860			285,966
Total Shareholders’ Equity	2,231,849			2,693,231
Total Liabilities and Shareholders’ Equity	2,983,709			2,979,197
Non-Guarantor Companies [Member]
CURRENT ASSETS
Cash and equivalents	21,054			37,429	36,090		36,375
Accounts receivable, net of allowances	55,687			69,729
Contract costs and recognized income not yet billed, net of progress payments	1,093			410
Inventories	67,835			66,373
Prepaid and other current assets	5,761			6,168
Assets of discontinued operations	324			324
Total Current Assets	151,754			180,433
PROPERTY, PLANT AND EQUIPMENT, net	40,398			41,636
GOODWILL	45,062			71,242
INTANGIBLE ASSETS, net	86,592			77,672
INTERCOMPANY RECEIVABLE	66,931			(121,445)
EQUITY INVESTMENTS IN SUBSIDIARIES	3,045,503			3,347,894
OTHER ASSETS	(2,079)			374
ASSETS OF DISCONTINUED OPERATIONS	2,901			2,916
Total Assets	3,437,062			3,600,722
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	7,312			7,337
Accounts payable and accrued liabilities	31,439			59,531
Liabilities of discontinued operations	11,657			29,537
Total Current Liabilities	50,408			96,405
LONG-TERM DEBT, net of debt discounts	55,586			57,890
INTERCOMPANY PAYABLES	421,184			263,227
OTHER LIABILITIES	17,401			20,592
LIABILITIES OF DISCONTINUED OPERATIONS	2,307			2,647
Total Liabilities	546,886			440,761
Total Shareholders’ Equity	2,890,176			3,159,961
Total Liabilities and Shareholders’ Equity	3,437,062			3,600,722
Elimination [Member]
CURRENT ASSETS
Cash and equivalents	0			0	$ 0		$ 0
Accounts receivable, net of allowances	0			(24,105)
Contract costs and recognized income not yet billed, net of progress payments	0			0
Inventories	13			(81)
Prepaid and other current assets	2,372			2,461
Assets of discontinued operations	0			0
Total Current Assets	2,385			(21,725)
PROPERTY, PLANT AND EQUIPMENT, net	0			0
GOODWILL	0			0
INTANGIBLE ASSETS, net	0			0
INTERCOMPANY RECEIVABLE	(868,496)			(249,345)
EQUITY INVESTMENTS IN SUBSIDIARIES	(5,109,739)			(5,845,156)
OTHER ASSETS	(6,683)			(8,612)
ASSETS OF DISCONTINUED OPERATIONS	0			0
Total Assets	(5,982,533)			(6,124,838)
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	0			0
Accounts payable and accrued liabilities	2,444			(16,474)
Liabilities of discontinued operations	0			0
Total Current Liabilities	2,444			(16,474)
LONG-TERM DEBT, net of debt discounts	0			0
INTERCOMPANY PAYABLES	(859,302)			(251,525)
OTHER LIABILITIES	(3,650)			(3,647)
LIABILITIES OF DISCONTINUED OPERATIONS	0			0
Total Liabilities	(860,508)			(271,646)
Total Shareholders’ Equity	(5,122,025)			(5,853,192)
Total Liabilities and Shareholders’ Equity	$ (5,982,533)			$ (6,124,838)