BASIS OF PRESENTATION, CONSOLIDATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) £ in Millions	3 Months Ended				9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 GBP (£)	Jun. 30, 2019 USD ($) aircraft	Jun. 30, 2018 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2019 USD ($) Affiliates	Mar. 31, 2018 USD ($)	Jul. 24, 2019	Apr. 01, 2019 USD ($)
Item Affected [Line Items]
Restricted cash			$ 3,234,000		$ 0	$ 0
Allowance for doubtful accounts receivable			800,000		1,600,000	1,600,000
Inventory allowance			19,100,000		19,400,000	19,400,000
Short-term portion of contract acquisition and pre-operating costs			9,600,000		9,800,000	9,800,000
Amortization of other deferred charges			2,400,000	$ 2,700,000
Goodwill			18,212,000		18,436,000	18,436,000
Long-term portion of contract acquisition and pre-operating costs			34,000,000		37,100,000	37,100,000
Deferred OEM cost recovery			$ 0		3,997,000	3,997,000
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			10
Other accrued liabilities			$ 32,773,000		38,679,000	38,679,000
Loss on sale of subsidiaries			(56,303,000)	0
Operating lease right-of-use assets			187,961,000		0	0
Total operating lease liabilities			$ 194,513,000
Accounting Standards Update 2016-02 [Member]
Item Affected [Line Items]
Operating lease right-of-use assets									$ 281,000,000
Total operating lease liabilities									$ 285,300,000
Eastern Airways International Limited [Member]
Item Affected [Line Items]
Cash Outflow for Termination of Business Acquisition | £		£ 17.1
Purchase Covenants, Non Solicitation Of Key Employees Period		12 months	12 months
Purchase Covenants, Right To Appoint Observer To Board Of Directors Period		12 months	12 months
Purchase Covenants, Transition Services Coverage Period		12 months	12 months
Bankruptcy Event [Member]
Item Affected [Line Items]
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			4
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							13,900,000
OEM Cost recoveries | Rent Expense
Item Affected [Line Items]
Offset Amount, Expense			$ 1,000,000	3,500,000	3,400,000		$ 16,600,000
OEM Cost recoveries | Rent Expense | Bankruptcy Event [Member]
Item Affected [Line Items]
Offset Amount, Expense			6,000,000
OEM Cost recoveries | Revenue
Item Affected [Line Items]
Former Gain Contingency, Recognized in Current Period				7,600,000
OEM Cost recoveries | Direct cost
Item Affected [Line Items]
Former Gain Contingency, Recognized in Current Period				$ 1,100,000
Effect on Future Earnings, Offset Amount					(2,300,000)
Affiliated entity
Item Affected [Line Items]
Allowance for doubtful accounts receivable			0		$ 0	$ 0
Aviashelf Aviation Co. [Member]
Item Affected [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent					48.50%	48.50%
Number Of Joint Ventures | Affiliates						2
Option To Acquire Additional Interest in Affiliate						8.50%
Proceeds from Divestiture of Businesses			2,600,000
Aviashelf Aviation Co. [Member] | Subsequent Event [Member]
Item Affected [Line Items]
Proceeds from Divestiture of Businesses	$ 400,000
Bristow Helicopter Leasing [Member]
Item Affected [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent					60.00%	60.00%
Proceeds from Divestiture of Businesses			1,400,000
8.75% Senior Secured Notes due 2023 | Subsequent Event [Member]
Item Affected [Line Items]
Bankruptcy, Restructuring Support Agreement, Percentage of Noteholders								99.30%
6.25% Senior Notes and 4.5% Convertible Senior Notes [Member] | Subsequent Event [Member]
Item Affected [Line Items]
Bankruptcy, Restructuring Support Agreement, Percentage of Noteholders								73.60%
Eastern Airways International Limited [Member]
Item Affected [Line Items]
Loss on sale of subsidiaries			(46,852,000)
Write Off Of Net Assets			35,000,000
Write Off Of Cumulative Translation Adjustment			11,900,000
Aviashelf and Bristow Helicopters Leasing Limited [Member]
Item Affected [Line Items]
Loss on sale of subsidiaries			(9,451,000)
Write Off Of Net Assets			2,300,000
Write Off Of Cumulative Translation Adjustment			$ 7,200,000