CONSOLIDATING GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details) - Summary of Condensed Consolidating Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
CURRENT ASSETS
Cash and equivalents	$ 236,456	$ 47,681	$ 47,425	$ 47,425	$ 72,553
Accounts receivable, net of allowances	271,966	208,229
Contract costs and recognized income not yet billed, net of progress payments	122,156	131,662
Inventories, net	384,467	299,437
Prepaid and other current assets	47,160	40,067
Assets of discontinued operations	0	370,724
Assets of discontinued operations not held for sale	328	329
Total Current Assets	1,062,533	1,098,129
PROPERTY, PLANT AND EQUIPMENT, net	291,516	232,135
GOODWILL	422,473	319,139
INTANGIBLE ASSETS, net	286,156	205,127
INTERCOMPANY RECEIVABLE	0	0
EQUITY INVESTMENTS IN SUBSIDIARIES	0	0
OTHER ASSETS	15,670	16,051
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	2,952	2,960
Total Assets	2,081,300	1,873,541
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	12,917	11,078
Accounts payable and accrued liabilities	369,493	267,209
Liabilities of discontinued operations	0	84,450
Liabilities of discontinued operations not held for sale	50,927	8,342
Total Current Liabilities	433,337	371,079
LONG-TERM DEBT, net of debt discounts	1,078,462	968,080
INTERCOMPANY PAYABLES	0	0
OTHER LIABILITIES	90,458	132,537
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	5,025	3,037
Total Liabilities	1,607,282	1,474,733
Total Shareholders’ Equity	474,018	398,808
Total Liabilities and Shareholders’ Equity	2,081,300	1,873,541
Parent Company [Member]
CURRENT ASSETS
Cash and equivalents	177,429	3,240		1,416	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	15,481	21,131
Assets of discontinued operations		0
Assets of discontinued operations not held for sale	0	0
Total Current Assets	192,910	24,371
PROPERTY, PLANT AND EQUIPMENT, net	863	645
GOODWILL	0	0
INTANGIBLE ASSETS, net	93	93
INTERCOMPANY RECEIVABLE	148,879	552,017
EQUITY INVESTMENTS IN SUBSIDIARIES	1,253,347	863,149
OTHER ASSETS	6,519	12,171
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Assets	1,602,611	1,452,446
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	2,276	2,854
Accounts payable and accrued liabilities	82,647	14,683
Liabilities of discontinued operations		0
Liabilities of discontinued operations not held for sale	0	0
Total Current Liabilities	84,923	17,537
LONG-TERM DEBT, net of debt discounts	1,038,901	903,609
INTERCOMPANY PAYABLES	45,285	84,068
OTHER LIABILITIES	(19,016)	48,424
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Liabilities	1,150,093	1,053,638
Total Shareholders’ Equity	452,518	398,808
Total Liabilities and Shareholders’ Equity	1,602,611	1,452,446
Guarantor Companies [Member]
CURRENT ASSETS
Cash and equivalents	22,937	8,066		7,405	27,692
Accounts receivable, net of allowances	224,997	168,731
Contract costs and recognized income not yet billed, net of progress payments	121,883	131,383
Inventories, net	318,101	246,605
Prepaid and other current assets	16,069	15,854
Assets of discontinued operations		168,306
Assets of discontinued operations not held for sale	0	0
Total Current Assets	703,987	738,945
PROPERTY, PLANT AND EQUIPMENT, net	247,766	200,362
GOODWILL	350,157	280,797
INTANGIBLE ASSETS, net	213,888	143,415
INTERCOMPANY RECEIVABLE	370,725	757,608
EQUITY INVESTMENTS IN SUBSIDIARIES	970,149	877,641
OTHER ASSETS	12,611	12,054
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Assets	2,869,283	3,010,822
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	5,425	1,471
Accounts payable and accrued liabilities	236,825	199,784
Liabilities of discontinued operations		47,426
Liabilities of discontinued operations not held for sale	0	0
Total Current Liabilities	242,250	248,681
LONG-TERM DEBT, net of debt discounts	7,787	6,044
INTERCOMPANY PAYABLES	47,811	1,259,413
OTHER LIABILITIES	80,712	76,036
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Liabilities	378,560	1,590,174
Total Shareholders’ Equity	2,490,723	1,420,648
Total Liabilities and Shareholders’ Equity	2,869,283	3,010,822
Non-Guarantor Companies [Member]
CURRENT ASSETS
Cash and equivalents	36,090	36,375		38,604	38,344
Accounts receivable, net of allowances	70,719	59,929
Contract costs and recognized income not yet billed, net of progress payments	273	279
Inventories, net	66,409	52,759
Prepaid and other current assets	9,611	3,002
Assets of discontinued operations		202,418
Assets of discontinued operations not held for sale	328	329
Total Current Assets	183,430	355,091
PROPERTY, PLANT AND EQUIPMENT, net	42,887	31,128
GOODWILL	72,316	38,342
INTANGIBLE ASSETS, net	72,175	61,619
INTERCOMPANY RECEIVABLE	(170,970)	915,551
EQUITY INVESTMENTS IN SUBSIDIARIES	3,143,462	1,613,891
OTHER ASSETS	(1,986)	(1,002)
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	2,952	2,960
Total Assets	3,344,266	3,017,580
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	5,216	6,753
Accounts payable and accrued liabilities	30,556	46,111
Liabilities of discontinued operations		37,024
Liabilities of discontinued operations not held for sale	50,927	8,342
Total Current Liabilities	86,699	98,230
LONG-TERM DEBT, net of debt discounts	31,774	58,427
INTERCOMPANY PAYABLES	244,621	854,518
OTHER LIABILITIES	11,853	14,135
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	5,025	3,037
Total Liabilities	379,972	1,028,347
Total Shareholders’ Equity	2,964,294	1,989,233
Total Liabilities and Shareholders’ Equity	3,344,266	3,017,580
Elimination [Member]
CURRENT ASSETS
Cash and equivalents	0	0		$ 0	$ 0
Accounts receivable, net of allowances	(23,750)	(20,431)
Contract costs and recognized income not yet billed, net of progress payments	0	0
Inventories, net	(43)	73
Prepaid and other current assets	5,999	80
Assets of discontinued operations		0
Assets of discontinued operations not held for sale	0	0
Total Current Assets	(17,794)	(20,278)
PROPERTY, PLANT AND EQUIPMENT, net	0	0
GOODWILL	0	0
INTANGIBLE ASSETS, net	0	0
INTERCOMPANY RECEIVABLE	(348,634)	(2,225,176)
EQUITY INVESTMENTS IN SUBSIDIARIES	(5,366,958)	(3,354,681)
OTHER ASSETS	(1,474)	(7,172)
ASSETS OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Assets	(5,734,860)	(5,607,307)
CURRENT LIABILITIES
Notes payable and current portion of long-term debt	0	0
Accounts payable and accrued liabilities	19,465	6,631
Liabilities of discontinued operations		0
Liabilities of discontinued operations not held for sale	0	0
Total Current Liabilities	19,465	6,631
LONG-TERM DEBT, net of debt discounts	0	0
INTERCOMPANY PAYABLES	(337,717)	(2,197,999)
OTHER LIABILITIES	16,909	(6,058)
LIABILITIES OF DISCONTINUED OPERATIONS NOT HELD FOR SALE	0	0
Total Liabilities	(301,343)	(2,197,426)
Total Shareholders’ Equity	(5,433,517)	(3,409,881)
Total Liabilities and Shareholders’ Equity	$ (5,734,860)	$ (5,607,307)