SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 855,108	$ 745,156	$ 1,688,008	$ 1,526,845
Revenue from Contract with Customer, Excluding Assessed Tax	838,304		1,653,970
Amortization of Acquired Contract Liabilities	16,804	27,898	34,038	57,371
Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	260,717	233,765	501,756	471,900
Revenue from Contract with Customer, Excluding Assessed Tax	249,814		479,351
Amortization of Acquired Contract Liabilities	8,768	9,299	17,617	16,602
Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	528,367	447,772	1,060,753	931,088
Revenue from Contract with Customer, Excluding Assessed Tax	518,374		1,040,337
Amortization of Acquired Contract Liabilities	8,036	18,599	16,421	40,769
Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	72,199	$ 68,366	138,414	$ 134,799
Revenue from Contract with Customer, Excluding Assessed Tax	70,116		134,282
Amortization of Acquired Contract Liabilities	0
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	585,310		1,162,373
Transferred over Time [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	72,188		136,547
Transferred over Time [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	448,315		901,594
Transferred over Time [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	64,807		124,232
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	252,994		491,597
Transferred at Point in Time [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	177,626		342,804
Transferred at Point in Time [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	70,059		138,743
Transferred at Point in Time [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,309		10,050
Total - Timing of Transfer [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	258,582		496,968
Total - Timing of Transfer [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	526,410		1,056,758
Total - Timing of Transfer [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	70,116		134,282
Commercial Aerospace [Member]
Disaggregation of Revenue [Line Items]
Revenues	432,832		885,042
Commercial Aerospace [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	133,103		253,680
Commercial Aerospace [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	244,636		526,799
Commercial Aerospace [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	55,093		104,563
Military [Member]
Disaggregation of Revenue [Line Items]
Revenues	166,086		316,085
Military [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	87,735		170,427
Military [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	66,482		124,404
Military [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	11,869		21,254
Business Jet [Member]
Disaggregation of Revenue [Line Items]
Revenues	207,562		389,239
Business Jet [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	15,297		28,133
Business Jet [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	191,866		359,313
Business Jet [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	399		1,793
Regional [Member]
Disaggregation of Revenue [Line Items]
Revenues	20,226		37,162
Regional [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	7,339		13,956
Regional [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	10,132		16,534
Regional [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,755		6,672
Non-aviation [Member]
Disaggregation of Revenue [Line Items]
Revenues	11,598		26,442
Non-aviation [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	6,340		13,155
Non-aviation [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,258		13,287
Non-aviation [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	0		0
Total - Sales Channel [Member] | Integrated Systems [Member]
Disaggregation of Revenue [Line Items]
Revenues	258,582		496,968
Total - Sales Channel [Member] | Aerospace Structures [Member]
Disaggregation of Revenue [Line Items]
Revenues	526,410		1,056,758
Total - Sales Channel [Member] | Product Support [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 70,116		$ 134,282