BASIS OF PRESENTATION, CONSOLIDATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2018	Mar. 31, 2017
Item Affected [Line Items]
Cash and cash equivalents		$ 231,326,000	$ 117,848,000	$ 231,326,000	$ 117,848,000				$ 380,223,000	$ 96,656,000
Allowance for doubtful accounts receivable		600,000		600,000					3,300,000
Allowance for Doubtful Accounts Receivable, Write-offs				2,300,000
Inventory allowance		21,100,000		21,100,000					26,000,000
Impairment of inventories		0	0	9,276,000	1,192,000
Short-term portion of contract acquisition and pre-operating costs		9,600,000		9,600,000					10,800,000
Amortization of other deferred charges		2,400,000	2,800,000	7,600,000	8,500,000
Goodwill		18,271,000		18,271,000					19,907,000
Accumulated goodwill impairment		50,861,000		50,861,000					50,861,000
Impairment of intangible assets		0	0	3,005,000	0
Long-term portion of contract acquisition and pre-operating costs		38,700,000		38,700,000					50,600,000
Impairment of property and equipment		0	0	104,939,000	0
Impairment charges on aircraft held for sale		1,350,000	1,560,000	1,350,000	11,307,000
Other accrued liabilities		38,692,000		38,692,000					65,978,000
Progress payments for aircraft		0	0	0	2,300,000
Accounting Standards Update 2016-16 [Member] | Retained Earnings
Item Affected [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		(1,700,000)		(1,700,000)
Accounting Standards Update 2017-07 [Member]
Item Affected [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results			$ 100,000		100,000
Bristow Academy [Member]
Item Affected [Line Items]
Impairment charges on aircraft held for sale					6,500,000
OEM Cost recoveries
Item Affected [Line Items]
Original Equipment Manufacturer, Recoveries Sought									136,000,000
Original Equipment Manufacturer, Amount Received				11,000,000					125,000,000
Accumulated Depreciation, Period Increase (Decrease)									(94,500,000)
Deferred OEM cost recovery		7,000,000		7,000,000					13,900,000
OEM Cost recoveries | Rent Expense
Item Affected [Line Items]
Offset Amount, Expense		1,000,000		6,900,000					16,600,000
Offset Amount, Expense, Remainder of Fiscal Year		1,000,000		1,000,000
Offset Amount, Expense, Rolling Year Two		4,000,000		4,000,000
Offset Amount, Expense, Rolling Year Three		2,000,000		2,000,000
OEM Cost recoveries | Revenue
Item Affected [Line Items]
Former Gain Contingency, Recognized in Current Period		7,600,000		7,600,000
OEM Cost recoveries | Direct cost
Item Affected [Line Items]
Former Gain Contingency, Recognized in Current Period		3,100,000		3,100,000
OEM Cost recoveries | Direct cost | Scenario, Forecast [Member]
Item Affected [Line Items]
Effect on Future Earnings, Offset Amount	$ (300,000)
Affiliated entity
Item Affected [Line Items]
Allowance for doubtful accounts receivable		$ 0		0					$ 0
Training Aircraft [Member]
Item Affected [Line Items]
Impairment of inventories					$ 1,200,000
H225 Aircraft [Member]
Item Affected [Line Items]
Impairment of inventories				8,900,000
Accumulated Depreciation, Period Increase (Decrease)				1,500,000
Impairment of property and equipment				87,500,000
H225 Aircraft [Member] | Depreciation Expense
Item Affected [Line Items]
Offset Amount, Expense				1,500,000
H225 Aircraft [Member] | Depreciation Expense | Scenario, Forecast [Member]
Item Affected [Line Items]
Effect on Future Earnings, Offset Amount	1,500,000					$ (10,300,000)	$ 1,900,000	$ 5,900,000
Other Aircraft Type [Member] | Scenario, Forecast [Member]
Item Affected [Line Items]
Accumulated Depreciation, Period Increase (Decrease)	$ 1,400,000							$ 2,800,000
Oil and Gas Properties [Member]
Item Affected [Line Items]
Impairment of property and equipment				0
Eastern Airways [Member]
Item Affected [Line Items]
Impairment of inventories				300,000
Impairment of intangible assets				3,005,000
Impairment of property and equipment				$ 17,500,000