SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 231,326			$ 380,223	$ 117,848			$ 96,656
Accounts receivable	217,827			246,980
Inventories	115,254			129,614
Assets held for sale	22,485			30,348
Prepaid expenses and other current assets	48,646			47,234
Total current assets	635,538			834,399
Intercompany investment	0			0
Investment in unconsolidated affiliates	113,974			126,170
Intercompany notes receivable	0			0
Land and buildings	240,201			250,040
Aircraft and equipment	2,479,543			2,511,131
Total property and equipment, at cost	2,719,744			2,761,171
Less – Accumulated depreciation and amortization	(872,201)			(693,151)
Total property and equipment, net	1,847,543			2,068,020
Goodwill	18,271			19,907
Other assets	116,418			116,506
Total assets	2,731,744			3,165,002
Accounts payable	91,916			101,270
Accrued liabilities	156,465			209,876
Short-term borrowings and current maturities of long-term debt	1,421,050			1,475,438
Total current liabilities	1,669,431			1,786,584
Long-term debt, less current maturities	9,174			11,096
Intercompany notes payable	0			0
Accrued pension liabilities	28,036			37,034
Other liabilities and deferred credits	28,573			36,952
Deferred taxes	119,057			115,192
Common stock	385			382
Additional paid-in capital	860,745			852,565
Retained earnings	524,846			788,834
Accumulated other comprehensive income (loss)	(330,944)			(286,094)
Treasury shares	(184,796)			(184,796)
Total Bristow Group stockholders’ investment	870,236			1,170,891
Noncontrolling interests	7,237			7,253
Total stockholders’ investment	877,473	$ 970,232	$ 1,120,644	1,178,144	1,249,016	$ 1,228,079	$ 1,245,841	1,289,283
Total liabilities and stockholders’ investment	2,731,744			3,165,002
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	(1,501)			0	(922)			0
Accounts receivable	(1,124,553)			(638,630)
Inventories	0			0
Assets held for sale	0			0
Prepaid expenses and other current assets	0			(1,643)
Total current assets	(1,126,054)			(640,273)
Intercompany investment	(2,110,202)			(2,445,623)
Investment in unconsolidated affiliates	0			0
Intercompany notes receivable	(274,288)			(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	(3,510,544)			(3,674,463)
Accounts payable	(1,115,618)			(616,909)
Accrued liabilities	(9,300)			(21,955)
Short-term borrowings and current maturities of long-term debt	0			0
Total current liabilities	(1,124,918)			(638,864)
Long-term debt, less current maturities	0			0
Intercompany notes payable	(275,391)			(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	(994,432)			(1,312,439)
Accumulated other comprehensive income (loss)	(666,055)			(729,264)
Treasury shares	0			0
Total Bristow Group stockholders’ investment	(2,110,235)			(2,491,451)
Noncontrolling interests	0			0
Total stockholders’ investment	(2,110,235)			(2,491,451)
Total liabilities and stockholders’ investment	(3,510,544)			(3,674,463)
Parent Company Only
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	155,167			277,176	27,895			3,382
Accounts receivable	506,745			211,412
Inventories	0			0
Assets held for sale	0			0
Prepaid expenses and other current assets	4,520			3,367
Total current assets	666,432			491,955
Intercompany investment	1,877,133			2,199,505
Investment in unconsolidated affiliates	0			0
Intercompany notes receivable	118,003			183,634
Land and buildings	4,806			4,806
Aircraft and equipment	155,628			156,651
Total property and equipment, at cost	160,434			161,457
Less – Accumulated depreciation and amortization	(46,012)			(39,780)
Total property and equipment, net	114,422			121,677
Goodwill	0			0
Other assets	4,786			4,966
Total assets	2,780,776			3,001,737
Accounts payable	413,795			341,342
Accrued liabilities	56,645			59,070
Short-term borrowings and current maturities of long-term debt	847,023			840,485
Total current liabilities	1,317,463			1,240,897
Long-term debt, less current maturities	0			0
Intercompany notes payable	103,449			132,740
Accrued pension liabilities	0			0
Other liabilities and deferred credits	10,732			14,078
Deferred taxes	68,416			77,373
Common stock	385			382
Additional paid-in capital	860,745			852,565
Retained earnings	524,846			788,834
Accumulated other comprehensive income (loss)	78,306			78,306
Treasury shares	(184,796)			(184,796)
Total Bristow Group stockholders’ investment	1,279,486			1,535,291
Noncontrolling interests	1,230			1,358
Total stockholders’ investment	1,280,716			1,536,649
Total liabilities and stockholders’ investment	2,780,776			3,001,737
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0			8,904	0			299
Accounts receivable	542,145			423,214
Inventories	34,658			31,300
Assets held for sale	18,506			26,737
Prepaid expenses and other current assets	2,674			4,494
Total current assets	597,983			494,649
Intercompany investment	104,436			104,435
Investment in unconsolidated affiliates	0			0
Intercompany notes receivable	9,229			36,358
Land and buildings	58,204			58,191
Aircraft and equipment	1,311,241			1,326,922
Total property and equipment, at cost	1,369,445			1,385,113
Less – Accumulated depreciation and amortization	(403,430)			(263,412)
Total property and equipment, net	966,015			1,121,701
Goodwill	0			0
Other assets	2,727			2,122
Total assets	1,680,390			1,759,265
Accounts payable	476,510			175,133
Accrued liabilities	(7,232)			6,735
Short-term borrowings and current maturities of long-term debt	271,279			296,782
Total current liabilities	740,557			478,650
Long-term debt, less current maturities	0			0
Intercompany notes payable	154,527			370,407
Accrued pension liabilities	0			0
Other liabilities and deferred credits	8,729			7,924
Deferred taxes	25,853			27,794
Common stock	4,996			4,996
Additional paid-in capital	29,387			29,387
Retained earnings	716,378			838,727
Accumulated other comprehensive income (loss)	(37)			1,380
Treasury shares	0			0
Total Bristow Group stockholders’ investment	750,724			874,490
Noncontrolling interests	0			0
Total stockholders’ investment	750,724			874,490
Total liabilities and stockholders’ investment	1,680,390			1,759,265
Non- Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	77,660			94,143	$ 90,875			$ 92,975
Accounts receivable	293,490			250,984
Inventories	80,596			98,314
Assets held for sale	3,979			3,611
Prepaid expenses and other current assets	41,452			41,016
Total current assets	497,177			488,068
Intercompany investment	128,633			141,683
Investment in unconsolidated affiliates	113,974			126,170
Intercompany notes receivable	147,056			368,575
Land and buildings	177,191			187,043
Aircraft and equipment	1,012,674			1,027,558
Total property and equipment, at cost	1,189,865			1,214,601
Less – Accumulated depreciation and amortization	(422,759)			(389,959)
Total property and equipment, net	767,106			824,642
Goodwill	18,271			19,907
Other assets	108,905			109,418
Total assets	1,781,122			2,078,463
Accounts payable	317,229			201,704
Accrued liabilities	116,352			166,026
Short-term borrowings and current maturities of long-term debt	302,748			338,171
Total current liabilities	736,329			705,901
Long-term debt, less current maturities	9,174			11,096
Intercompany notes payable	17,415			41,001
Accrued pension liabilities	28,036			37,034
Other liabilities and deferred credits	9,112			14,950
Deferred taxes	24,788			10,025
Common stock	131,317			131,317
Additional paid-in capital	284,048			284,048
Retained earnings	278,054			473,712
Accumulated other comprehensive income (loss)	256,842			363,484
Treasury shares	0			0
Total Bristow Group stockholders’ investment	950,261			1,252,561
Noncontrolling interests	6,007			5,895
Total stockholders’ investment	956,268			1,258,456
Total liabilities and stockholders’ investment	$ 1,781,122			$ 2,078,463