SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 307,791		$ 380,223	$ 97,343		$ 96,656
Accounts receivable	231,821		246,980
Inventories	117,706		129,614
Assets held for sale	24,176		30,348
Prepaid expenses and other current assets	46,603		47,234
Total current assets	728,097		834,399
Intercompany investment	0		0
Investment in unconsolidated affiliates	110,637		126,170
Intercompany notes receivable	0		0
Land and buildings	243,245		250,040
Aircraft and equipment	2,491,291		2,511,131
Total property and equipment, at cost	2,734,536		2,761,171
Less – Accumulated depreciation and amortization	(848,271)		(693,151)
Total property and equipment, net	1,886,265		2,068,020
Goodwill	18,778		19,907
Other assets	117,027		116,506
Total assets	2,860,804		3,165,002
Accounts payable	103,510		101,270
Accrued liabilities	174,909		204,927
Short-term borrowings and current maturities of long-term debt	50,798		56,700
Total current liabilities	329,217		362,897
Long-term debt, less current maturities	1,398,911		1,429,834
Intercompany notes payable	0		0
Accrued pension liabilities	28,484		37,034
Other liabilities and deferred credits	31,639		36,952
Deferred taxes	97,372		115,192
Common stock	385		382
Additional paid-in capital	858,809		852,565
Retained earnings	615,739		793,783
Accumulated other comprehensive income (loss)	(322,015)		(286,094)
Treasury shares	(184,796)		(184,796)
Total Bristow Group stockholders’ investment	968,122		1,175,840
Noncontrolling interests	7,059		7,253
Total stockholders’ investment	975,181	$ 1,125,593	1,183,093	1,233,028	$ 1,250,790	1,294,232
Total liabilities and stockholders’ investment	2,860,804		3,165,002
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0		0	0		0
Accounts receivable	(1,007,238)		(638,630)
Inventories	0		0
Assets held for sale	0		0
Prepaid expenses and other current assets	0		(1,643)
Total current assets	(1,007,238)		(640,273)
Intercompany investment	(2,140,322)		(2,450,572)
Investment in unconsolidated affiliates	0		0
Intercompany notes receivable	(293,343)		(588,567)
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
Goodwill	0		0
Other assets	0		0
Total assets	(3,440,903)		(3,679,412)
Accounts payable	(998,456)		(616,909)
Accrued liabilities	(7,738)		(21,955)
Short-term borrowings and current maturities of long-term debt	0		0
Total current liabilities	(1,006,194)		(638,864)
Long-term debt, less current maturities	0		0
Intercompany notes payable	(294,445)		(544,148)
Accrued pension liabilities	0		0
Other liabilities and deferred credits	0		0
Deferred taxes	0		0
Common stock	(136,313)		(136,313)
Additional paid-in capital	(313,435)		(313,435)
Retained earnings	(1,021,405)		(1,317,388)
Accumulated other comprehensive income (loss)	(669,111)		(729,264)
Treasury shares	0		0
Total Bristow Group stockholders’ investment	(2,140,264)		(2,496,400)
Noncontrolling interests	0		0
Total stockholders’ investment	(2,140,264)		(2,496,400)
Total liabilities and stockholders’ investment	(3,440,903)		(3,679,412)
Parent Company Only
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	236,075		277,176	591		3,382
Accounts receivable	438,878		211,412
Inventories	0		0
Assets held for sale	0		0
Prepaid expenses and other current assets	2,608		3,367
Total current assets	677,561		491,955
Intercompany investment	1,904,177		2,204,454
Investment in unconsolidated affiliates	0		0
Intercompany notes receivable	124,389		183,634
Land and buildings	4,806		4,806
Aircraft and equipment	157,378		156,651
Total property and equipment, at cost	162,184		161,457
Less – Accumulated depreciation and amortization	(45,937)		(39,780)
Total property and equipment, net	116,247		121,677
Goodwill	0		0
Other assets	4,303		4,966
Total assets	2,826,677		3,006,686
Accounts payable	397,602		341,342
Accrued liabilities	53,851		59,070
Short-term borrowings and current maturities of long-term debt	(3,541)		(3,334)
Total current liabilities	447,912		397,078
Long-term debt, less current maturities	848,103		843,819
Intercompany notes payable	105,791		132,740
Accrued pension liabilities	0		0
Other liabilities and deferred credits	12,177		14,078
Deferred taxes	42,991		77,373
Common stock	385		382
Additional paid-in capital	858,809		852,565
Retained earnings	615,739		793,783
Accumulated other comprehensive income (loss)	78,306		78,306
Treasury shares	(184,796)		(184,796)
Total Bristow Group stockholders’ investment	1,368,443		1,540,240
Noncontrolling interests	1,260		1,358
Total stockholders’ investment	1,369,703		1,541,598
Total liabilities and stockholders’ investment	2,826,677		3,006,686
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	1,131		8,904	771		299
Accounts receivable	508,873		423,214
Inventories	36,637		31,300
Assets held for sale	19,856		26,737
Prepaid expenses and other current assets	2,802		4,494
Total current assets	569,299		494,649
Intercompany investment	104,435		104,435
Investment in unconsolidated affiliates	0		0
Intercompany notes receivable	9,229		36,358
Land and buildings	58,089		58,191
Aircraft and equipment	1,317,739		1,326,922
Total property and equipment, at cost	1,375,828		1,385,113
Less – Accumulated depreciation and amortization	(384,448)		(263,412)
Total property and equipment, net	991,380		1,121,701
Goodwill	0		0
Other assets	2,026		2,122
Total assets	1,676,369		1,759,265
Accounts payable	428,348		175,133
Accrued liabilities	(5,771)		6,735
Short-term borrowings and current maturities of long-term debt	20,079		20,596
Total current liabilities	442,656		202,464
Long-term debt, less current maturities	258,590		276,186
Intercompany notes payable	168,885		370,407
Accrued pension liabilities	0		0
Other liabilities and deferred credits	7,253		7,924
Deferred taxes	27,343		27,794
Common stock	4,996		4,996
Additional paid-in capital	29,387		29,387
Retained earnings	736,924		838,727
Accumulated other comprehensive income (loss)	335		1,380
Treasury shares	0		0
Total Bristow Group stockholders’ investment	771,642		874,490
Noncontrolling interests	0		0
Total stockholders’ investment	771,642		874,490
Total liabilities and stockholders’ investment	1,676,369		1,759,265
Non- Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	70,585		94,143	$ 95,981		$ 92,975
Accounts receivable	291,308		250,984
Inventories	81,069		98,314
Assets held for sale	4,320		3,611
Prepaid expenses and other current assets	41,193		41,016
Total current assets	488,475		488,068
Intercompany investment	131,710		141,683
Investment in unconsolidated affiliates	110,637		126,170
Intercompany notes receivable	159,725		368,575
Land and buildings	180,350		187,043
Aircraft and equipment	1,016,174		1,027,558
Total property and equipment, at cost	1,196,524		1,214,601
Less – Accumulated depreciation and amortization	(417,886)		(389,959)
Total property and equipment, net	778,638		824,642
Goodwill	18,778		19,907
Other assets	110,698		109,418
Total assets	1,798,661		2,078,463
Accounts payable	276,016		201,704
Accrued liabilities	134,567		161,077
Short-term borrowings and current maturities of long-term debt	34,260		39,438
Total current liabilities	444,843		402,219
Long-term debt, less current maturities	292,218		309,829
Intercompany notes payable	19,769		41,001
Accrued pension liabilities	28,484		37,034
Other liabilities and deferred credits	12,209		14,950
Deferred taxes	27,038		10,025
Common stock	131,317		131,317
Additional paid-in capital	284,048		284,048
Retained earnings	284,481		478,661
Accumulated other comprehensive income (loss)	268,455		363,484
Treasury shares	0		0
Total Bristow Group stockholders’ investment	968,301		1,257,510
Noncontrolling interests	5,799		5,895
Total stockholders’ investment	974,100		1,263,405
Total liabilities and stockholders’ investment	$ 1,798,661		$ 2,078,463