SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 153,885		$ 178,055
Restricted cash	38,910		0
Accounts receivable	228,793		216,791
Inventories	113,514		121,308
Assets held for sale	0		5,350
Prepaid expenses and other current assets	42,545		44,009
Total current assets	577,647		565,513
Intercompany investment	0		0
Investment in unconsolidated affiliates	109,986		118,203
Intercompany notes receivable	0		0
Land and buildings	238,208		244,273
Aircraft and equipment	2,403,726		2,497,622
Total property and equipment, at cost	2,641,934		2,741,895
Less – Accumulated depreciation and amortization	(963,634)		(907,715)
Total property and equipment, net	1,678,300		1,834,180
Right-of-use asset	331,743		0
Goodwill	0		18,436
Other assets	94,899		116,267
Total assets	2,792,575		2,652,599
Accounts payable	93,433		99,573
Accrued liabilities	232,589		150,648
Short-term borrowings and current maturities of long-term debt	947,041		1,418,630
Total current liabilities	1,273,063		1,668,851
Long-term debt, less current maturities	75,611		8,223
Long-term Debt, Current Maturities	947,041		1,418,630
Intercompany notes payable	0		0
Accrued pension liabilities	18,706		25,726
Other liabilities and deferred credits	7,905		26,229
Deferred taxes	59,862		111,203
Long-term operating lease liabilities	251,399		0
Liabilities subject to compromise	624,867		0
Common stock	386		386
Additional paid-in capital	863,546		862,020
Retained earnings	123,378		455,598
Accumulated other comprehensive income (loss)	(321,802)		(327,989)
Treasury shares	(184,796)		(184,796)
Total Bristow Group stockholders’ investment	480,712		805,219
Noncontrolling interests	450		7,148
Total stockholders’ investment	481,162	$ 655,842	812,367	$ 976,076	$ 1,126,245	$ 1,183,501
Total liabilities and stockholders’ investment	2,792,575		2,652,599
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0		0
Restricted cash	0
Accounts receivable	(1,369,206)		(1,190,445)
Inventories	0		0
Assets held for sale	0		0
Prepaid expenses and other current assets	0		0
Total current assets	(1,369,206)		(1,190,445)
Intercompany investment	(1,847,445)		(2,058,314)
Investment in unconsolidated affiliates	0		0
Intercompany notes receivable	(261,486)		(280,220)
Land and buildings	0		0
Aircraft and equipment	0		0
Total property and equipment, at cost	0		0
Less – Accumulated depreciation and amortization	0		0
Total property and equipment, net	0		0
Right-of-use asset	(40,061)
Goodwill	0		0
Other assets	0		0
Total assets	(3,518,198)		(3,528,979)
Accounts payable	(1,355,479)		(1,180,270)
Accrued liabilities	(52,569)		(10,049)
Short-term borrowings and current maturities of long-term debt	0		0
Total current liabilities	(1,408,048)		(1,190,319)
Long-term debt, less current maturities	0		0
Intercompany notes payable	(261,486)		(280,220)
Accrued pension liabilities	0		0
Other liabilities and deferred credits	0		0
Deferred taxes	0		0
Long-term operating lease liabilities	(1,027)
Liabilities subject to compromise	0
Common stock	(136,313)		(136,313)
Additional paid-in capital	(313,484)		(313,435)
Retained earnings	(742,641)		(946,730)
Accumulated other comprehensive income (loss)	(655,199)		(661,962)
Treasury shares	0		0
Total Bristow Group stockholders’ investment	(1,847,637)		(2,058,440)
Noncontrolling interests	0		0
Total stockholders’ investment	(1,847,637)		(2,058,440)
Total liabilities and stockholders’ investment	(3,518,198)		(3,528,979)
Parent Company Only
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	31,268		90,586
Restricted cash	33
Accounts receivable	644,260		535,502
Inventories	0		0
Assets held for sale	0		0
Prepaid expenses and other current assets	8,261		3,734
Total current assets	683,822		629,822
Intercompany investment	1,625,547		1,829,271
Investment in unconsolidated affiliates	0		0
Intercompany notes receivable	135,327		140,659
Land and buildings	4,806		4,807
Aircraft and equipment	158,399		155,667
Total property and equipment, at cost	163,205		160,474
Less – Accumulated depreciation and amortization	(53,874)		(47,546)
Total property and equipment, net	109,331		112,928
Right-of-use asset	23
Goodwill	0		0
Other assets	3,859		3,563
Total assets	2,557,909		2,716,243
Accounts payable	510,741		441,485
Accrued liabilities	72,863		51,071
Short-term borrowings and current maturities of long-term debt	380,902		849,524
Total current liabilities	964,506		1,342,080
Long-term debt, less current maturities	34,161		0
Intercompany notes payable	88,573		91,664
Accrued pension liabilities	0		0
Other liabilities and deferred credits	4,548		10,430
Deferred taxes	14,224		59,302
Long-term operating lease liabilities	0
Liabilities subject to compromise	569,804
Common stock	386		386
Additional paid-in capital	863,546		862,020
Retained earnings	123,378		455,598
Accumulated other comprehensive income (loss)	78,306		78,306
Treasury shares	(184,796)		(184,796)
Total Bristow Group stockholders’ investment	880,820		1,211,514
Noncontrolling interests	1,273		1,253
Total stockholders’ investment	882,093		1,212,767
Total liabilities and stockholders’ investment	2,557,909		2,716,243
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	7,516		3,205
Restricted cash	0
Accounts receivable	679,196		583,912
Inventories	35,658		35,331
Assets held for sale	0		5,541
Prepaid expenses and other current assets	1,686		1,001
Total current assets	724,056		628,990
Intercompany investment	97,435		97,435
Investment in unconsolidated affiliates	0		0
Intercompany notes receivable	11,151		11,151
Land and buildings	58,204		58,204
Aircraft and equipment	1,277,861		1,312,115
Total property and equipment, at cost	1,336,065		1,370,319
Less – Accumulated depreciation and amortization	(497,745)		(419,983)
Total property and equipment, net	838,320		950,336
Right-of-use asset	54,625
Goodwill	0		0
Other assets	4,047		3,410
Total assets	1,729,634		1,691,322
Accounts payable	597,832		510,911
Accrued liabilities	22,702		(9,807)
Short-term borrowings and current maturities of long-term debt	253,294		268,559
Total current liabilities	873,828		769,663
Long-term debt, less current maturities	0		0
Intercompany notes payable	143,233		155,643
Accrued pension liabilities	0		0
Other liabilities and deferred credits	0		8,613
Deferred taxes	26,065		26,268
Long-term operating lease liabilities	32,060
Liabilities subject to compromise	35,000
Common stock	4,996		4,996
Additional paid-in capital	29,387		29,387
Retained earnings	585,065		696,397
Accumulated other comprehensive income (loss)	0		355
Treasury shares	0		0
Total Bristow Group stockholders’ investment	619,448		731,135
Noncontrolling interests	0		0
Total stockholders’ investment	619,448		731,135
Total liabilities and stockholders’ investment	1,729,634		1,691,322
Non- Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	115,101		84,264
Restricted cash	38,877
Accounts receivable	274,543		287,822
Inventories	77,856		85,977
Assets held for sale	0		(191)
Prepaid expenses and other current assets	32,598		39,274
Total current assets	538,975		497,146
Intercompany investment	124,463		131,608
Investment in unconsolidated affiliates	109,986		118,203
Intercompany notes receivable	115,008		128,410
Land and buildings	175,198		181,262
Aircraft and equipment	967,466		1,029,840
Total property and equipment, at cost	1,142,664		1,211,102
Less – Accumulated depreciation and amortization	(412,015)		(440,186)
Total property and equipment, net	730,649		770,916
Right-of-use asset	317,156
Goodwill	0		18,436
Other assets	86,993		109,294
Total assets	2,023,230		1,774,013
Accounts payable	340,339		327,447
Accrued liabilities	189,593		119,433
Short-term borrowings and current maturities of long-term debt	312,845		300,547
Total current liabilities	842,777		747,427
Long-term debt, less current maturities	41,450		8,223
Intercompany notes payable	29,680		32,913
Accrued pension liabilities	18,706		25,726
Other liabilities and deferred credits	3,357		7,186
Deferred taxes	19,573		25,633
Long-term operating lease liabilities	220,366
Liabilities subject to compromise	20,063
Common stock	131,317		131,317
Additional paid-in capital	284,097		284,048
Retained earnings	157,576		250,333
Accumulated other comprehensive income (loss)	255,091		255,312
Treasury shares	0		0
Total Bristow Group stockholders’ investment	828,081		921,010
Noncontrolling interests	(823)		5,895
Total stockholders’ investment	827,258		926,905
Total liabilities and stockholders’ investment	$ 2,023,230		$ 1,774,013