COMMITMENTS AND CONTINGENCIES - Environmental Contingencies, Other Purchase Obligations and Other Matters (Details) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Feb. 28, 2018 aircraft	Dec. 31, 2017 USD ($) aircraft Facility	Dec. 31, 2017 USD ($) aircraft Facility
Other Commitments [Line Items]
Number of former waste disposal facilities | Facility		3	3
Number Of Lease Return To Lessor		3
Low
Other Commitments [Line Items]
Estimate of possible loss | $		$ 4.0	$ 4.0
High
Other Commitments [Line Items]
Estimate of possible loss | $		6.0	6.0
Subsequent Event
Other Commitments [Line Items]
Number Of Lease Return To Lessor	1
OEM Cost recoveries
Other Commitments [Line Items]
Original Equipment Manufacturer, Recoveries Sought | $		130.0	130.0
Original Equipment Manufacturer, Amount Received | $		$ 125.0	$ 125.0
UNITED KINGDOM
Other Commitments [Line Items]
Number Of Lease Return To Lessor		1
UNITED KINGDOM | Subsequent Event
Other Commitments [Line Items]
Number Of Lease Return To Lessor	1
AUSTRALIA
Other Commitments [Line Items]
Number Of Lease Return To Lessor		2
H225 Super Puma | NORWAY | Commercial Type Aircraft
Other Commitments [Line Items]
Number of aircraft suspend operations			1
H225 Super Puma | NORWAY | Search And Rescue Type Aircraft
Other Commitments [Line Items]
Number of aircraft suspend operations			4
H225 Super Puma | UNITED KINGDOM | Commercial Type Aircraft
Other Commitments [Line Items]
Number of aircraft suspend operations			13
H225 Super Puma | AUSTRALIA | Commercial Type Aircraft
Other Commitments [Line Items]
Number of aircraft suspend operations			6
H225 Super Puma | AUSTRALIA | Search And Rescue Type Aircraft
Other Commitments [Line Items]
Number of aircraft suspend operations			3
AW189
Other Commitments [Line Items]
Number of aircraft delivery delayed			4
Other Commitments
Other Commitments [Line Items]
Purchase obligations | $		$ 28.4	$ 28.4