CONSOLIDATING GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details) - Summary of Condensed Consolidating Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016
CURRENT ASSETS
Cash and equivalents	$ 63,766	$ 47,681	$ 69,448	$ 72,553
Accounts receivable, net of allowances	311,129	208,229
Contract costs and recognized income not yet billed, net of progress payments	110,138	131,662
Inventories, net	395,813	299,437
Prepaid and other current assets	56,955	40,067
Assets of discontinued operations	0	370,724
Assets of discontinued operations not held for sale	326	329
Total Current Assets	938,127	1,098,129
PROPERTY, PLANT AND EQUIPMENT, net	325,078	232,135
GOODWILL	502,055	319,139
INTANGIBLE ASSETS, net	316,956	205,127
INTERCOMPANY RECEIVABLE	0	0
EQUITY INVESTMENTS IN SUBSIDIARIES	0	0
OTHER ASSETS	16,505	16,051
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	2,930	2,960
Total Assets	2,101,651	1,873,541
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	10,739	11,078
Accounts payable and accrued liabilities	378,996	267,209
Liabilities of discontinued operations	0	84,450
Liabilities of discontinued operations not held for sale	25,795	8,342
Total Current Liabilities	415,530	371,079
LONG-TERM DEBT, net of debt discounts	1,124,981	968,080
INTERCOMPANY PAYABLES	0	0
OTHER LIABILITIES	90,127	132,537
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	4,926	3,037
Total Liabilities	1,635,564	1,474,733
Total Shareholders’ Equity	466,087	398,808
Total Liabilities and Shareholders’ Equity	2,101,651	1,873,541
Parent Company [Member]
CURRENT ASSETS
Cash and equivalents	8,589	3,240	21,231	6,517
Accounts receivable, net of allowances	0	0
Contract costs and recognized income not yet billed, net of progress payments	0	0
Inventories, net	0	0
Prepaid and other current assets	19,966	21,131
Assets of discontinued operations		0
Assets of discontinued operations not held for sale	0	0
Total Current Assets	28,555	24,371
PROPERTY, PLANT AND EQUIPMENT, net	921	645
GOODWILL	0	0
INTANGIBLE ASSETS, net	93	93
INTERCOMPANY RECEIVABLE	120,061	552,017
EQUITY INVESTMENTS IN SUBSIDIARIES	1,481,220	863,149
OTHER ASSETS	7,057	12,171
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Assets	1,637,907	1,452,446
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	2,276	2,854
Accounts payable and accrued liabilities	43,385	14,683
Liabilities of discontinued operations		0
Liabilities of discontinued operations not held for sale	0	0
Total Current Liabilities	45,661	17,537
LONG-TERM DEBT, net of debt discounts	1,088,501	903,609
INTERCOMPANY PAYABLES	54,070	84,068
OTHER LIABILITIES	(16,412)	48,424
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Liabilities	1,171,820	1,053,638
Total Shareholders’ Equity	466,087	398,808
Total Liabilities and Shareholders’ Equity	1,637,907	1,452,446
Guarantor Companies [Member]
CURRENT ASSETS
Cash and equivalents	18,470	8,066	11,550	27,692
Accounts receivable, net of allowances	270,289	168,731
Contract costs and recognized income not yet billed, net of progress payments	109,655	131,383
Inventories, net	334,225	246,605
Prepaid and other current assets	20,385	15,854
Assets of discontinued operations		168,306
Assets of discontinued operations not held for sale	0	0
Total Current Assets	753,024	738,945
PROPERTY, PLANT AND EQUIPMENT, net	283,228	200,362
GOODWILL	431,934	280,797
INTANGIBLE ASSETS, net	238,691	143,415
INTERCOMPANY RECEIVABLE	293,261	757,608
EQUITY INVESTMENTS IN SUBSIDIARIES	969,246	877,641
OTHER ASSETS	12,897	12,054
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Assets	2,982,281	3,010,822
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	3,351	1,471
Accounts payable and accrued liabilities	274,687	199,784
Liabilities of discontinued operations		47,426
Liabilities of discontinued operations not held for sale	9,071	0
Total Current Liabilities	287,109	248,681
LONG-TERM DEBT, net of debt discounts	6,953	6,044
INTERCOMPANY PAYABLES	(45,790)	1,259,413
OTHER LIABILITIES	72,827	76,036
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Liabilities	321,099	1,590,174
Total Shareholders’ Equity	2,661,182	1,420,648
Total Liabilities and Shareholders’ Equity	2,982,281	3,010,822
Non-Guarantor Companies [Member]
CURRENT ASSETS
Cash and equivalents	36,707	36,375	36,667	38,344
Accounts receivable, net of allowances	64,953	59,929
Contract costs and recognized income not yet billed, net of progress payments	483	279
Inventories, net	61,675	52,759
Prepaid and other current assets	10,591	3,002
Assets of discontinued operations		202,418
Assets of discontinued operations not held for sale	326	329
Total Current Assets	174,735	355,091
PROPERTY, PLANT AND EQUIPMENT, net	40,929	31,128
GOODWILL	70,121	38,342
INTANGIBLE ASSETS, net	78,172	61,619
INTERCOMPANY RECEIVABLE	(110,351)	915,551
EQUITY INVESTMENTS IN SUBSIDIARIES	3,305,421	1,613,891
OTHER ASSETS	(1,954)	(1,002)
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	2,930	2,960
Total Assets	3,560,003	3,017,580
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	5,112	6,753
Accounts payable and accrued liabilities	69,493	46,111
Liabilities of discontinued operations		37,024
Liabilities of discontinued operations not held for sale	16,724	8,342
Total Current Liabilities	91,329	98,230
LONG-TERM DEBT, net of debt discounts	29,527	58,427
INTERCOMPANY PAYABLES	303,269	854,518
OTHER LIABILITIES	16,800	14,135
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	4,926	3,037
Total Liabilities	445,851	1,028,347
Total Shareholders’ Equity	3,114,152	1,989,233
Total Liabilities and Shareholders’ Equity	3,560,003	3,017,580
Elimination [Member]
CURRENT ASSETS
Cash and equivalents	0	0	$ 0	$ 0
Accounts receivable, net of allowances	(24,113)	(20,431)
Contract costs and recognized income not yet billed, net of progress payments	0	0
Inventories, net	(87)	73
Prepaid and other current assets	6,013	80
Assets of discontinued operations		0
Assets of discontinued operations not held for sale	0	0
Total Current Assets	(18,187)	(20,278)
PROPERTY, PLANT AND EQUIPMENT, net	0	0
GOODWILL	0	0
INTANGIBLE ASSETS, net	0	0
INTERCOMPANY RECEIVABLE	(302,971)	(2,225,176)
EQUITY INVESTMENTS IN SUBSIDIARIES	(5,755,887)	(3,354,681)
OTHER ASSETS	(1,495)	(7,172)
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Assets	(6,078,540)	(5,607,307)
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	0	0
Accounts payable and accrued liabilities	(8,569)	6,631
Liabilities of discontinued operations		0
Liabilities of discontinued operations not held for sale	0	0
Total Current Liabilities	(8,569)	6,631
LONG-TERM DEBT, net of debt discounts	0	0
INTERCOMPANY PAYABLES	(311,549)	(2,197,999)
OTHER LIABILITIES	16,912	(6,058)
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Liabilities	(303,206)	(2,197,426)
Total Shareholders’ Equity	(5,775,334)	(3,409,881)
Total Liabilities and Shareholders’ Equity	$ (6,078,540)	$ (5,607,307)