COMMITMENTS AND CONTINGENCIES Ligitgation, Environmental, Other Purchase Contracts and Other (Details) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2009 aircraft	Mar. 31, 2018 USD ($) aircraft Facility	Mar. 31, 2017 aircraft	Mar. 31, 2016 aircraft	Mar. 31, 2015 aircraft	Oct. 31, 2008 aircraft
Loss Contingencies [Line Items]
Site Contingency, Number of Locations | Facility			3
Number Of Aircraft Suspend Operations			24
Number Of Aircraft Delivery Delayed			4
Minimum
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss | $			$ 5.0
Maximum
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss | $			6.0
Original Equipment Manufacturer Cost Recoveries
Loss Contingencies [Line Items]
Original Equipment Manufacturer, Recoveries Sought | $			136.0
Original Equipment Manufacturer, Amount Received | $			125.0
Other commitments
Loss Contingencies [Line Items]
Unrecorded unconditional purchase obligation | $			$ 48.3
Subsequent Event | Original Equipment Manufacturer Cost Recoveries
Loss Contingencies [Line Items]
Original Equipment Manufacturer, Amount Received | $	$ 11.0
Options
Loss Contingencies [Line Items]
Number Of Aircraft Balance			4	4	14	30
Exercised options			0	0	0
Expired Options			0	10	20
Options | Bristow Norway
Loss Contingencies [Line Items]
Number Of Aircraft Balance							5
Exercised options		1
Expired Options			2