SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Costs and Expenses	$ 824,828		$ 929,452	$ 2,581,385	$ 2,457,325
Restructuring and Related Cost, Incurred Cost	2,327		6,531	18,206	36,289	$ 195,300
Gain (Loss) on Disposition of Business	0		0	(17,837)	(20,371)
Operating Income (Loss)	(16,933)		(154,206)	(85,482)	(155,234)
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	(16,520)		(34,502)	(49,581)	(72,787)
Interest expense and other	29,309		25,836	83,515	72,229
Income (loss) from continuing operations before income taxes	(29,722)		(145,540)	(119,416)	(154,676)
Depreciation and amortization	37,404		39,320	114,349	119,318
Asset Impairment Charges	0		190,227	0	190,227
Amortization of Acquired Contract Liabilities	14,731		34,492	48,769	91,862
EBITDA	5,740		40,849	85,176	82,820
Capital expenditures	10,570		9,157	34,824	31,932
Total assets	3,330,514			3,330,514		3,807,064
Revenues	807,895		775,246	2,495,903	2,302,091
Corporate Segment [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	0		2,382	2,767	17,089
Integrated Systems [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	2,150		1,337	5,206	3,678
Operating Income (Loss)	39,947		42,216	115,221	130,839
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	452				(1,332)
Depreciation and amortization	7,376		8,318	22,316	27,857
Amortization of Acquired Contract Liabilities	8,172		11,634	25,789	28,235
EBITDA	39,151		38,900	111,748	130,461
Capital expenditures	3,951		1,903	9,388	5,923
Total assets	1,231,882			1,231,882		1,225,770
Revenues	252,437		239,198	754,193	711,099
Aerospace Structures [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	177		2,793	10,070	14,743
Operating Income (Loss)	(49,813)		(193,155)	(152,143)	(224,726)
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component			18,951		(56,879)
Depreciation and amortization	27,673		28,898	84,888	85,342
Asset Impairment Charges	0		190,227	0	190,227
Amortization of Acquired Contract Liabilities	6,559		22,858	22,980	63,627
EBITDA	(28,699)		3,112	(2,994)	(12,784)
Capital expenditures	5,722		5,791	22,937	22,066
Total assets	1,784,185			1,784,185		2,260,416
Revenues	490,337		473,273	1,551,090	1,404,359
Product Support [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	0		19	163	779
Operating Income (Loss)	11,421		12,399	30,604	32,069
Depreciation and amortization	1,611		1,663	4,944	5,068
Amortization of Acquired Contract Liabilities	0
EBITDA	13,032		14,062	35,548	37,137
Capital expenditures	852		599	1,871	1,629
Total assets	283,343			283,343		281,101
Revenues	71,446		68,039	209,860	202,839
Elimination of inter-segment sales
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Revenues	(6,325)		(5,264)	(19,240)	(16,206)
Corporate
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Operating Income (Loss)	(18,488)		(15,666)	(79,164)	(93,416)
Depreciation and amortization	744		441	2,201	1,051
EBITDA	(17,744)		(15,225)	(59,126)	(71,994)
Capital expenditures	45		864	628	2,314
Total assets	31,104			31,104		39,777
Restructuring Charges [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	2,327		6,149	18,206	33,751
Restructuring Charges [Member] | Corporate Segment [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	0		2,382	2,767	17,089
Restructuring Charges [Member] | Integrated Systems [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	2,150		955	5,206	1,769
Restructuring Charges [Member] | Aerospace Structures [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	177		2,793	10,070	14,114
Restructuring Charges [Member] | Product Support [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Restructuring and Related Cost, Incurred Cost	0		19	163	779
Guarantor Subsidiaries [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Costs and Expenses	741,002		781,391	2,309,008	2,096,962
Gain (Loss) on Disposition of Business	0		0	(947)	0
Operating Income (Loss)	(5,249)		(75,599)	(22,076)	(68)
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	(16,188)		(18,771)	(48,562)	(56,344)
Interest expense and other	4,007		2,796	13,334	8,181
Income (loss) from continuing operations before income taxes	(30,552)		(98,501)	(99,129)	(67,981)
Depreciation and amortization	32,640		34,606	99,302	105,781
Capital expenditures				30,398	25,507
Total assets	2,627,915			2,627,915		$ 3,123,793
Revenues	735,753		705,792	2,286,932	2,096,894
Accounting Standards Update 2017-07 [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		$ 87,241
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component			(34,502)		(72,787)
Non-US [Member]
Financial information of reportable segment and the reconciliation of EBITDA to operating income
Revenues	$ 245,505		$ 184,182	$ 736,501	$ 529,226