BASIS OF PRESENTATION, CONSOLIDATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Immaterial Corrections to Prior Period Financial Information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term debt, less current maturities	$ 9,778		$ 11,096
Accrued wages, benefits and related taxes	51,960		67,334
Retained earnings	610,790		788,834
Total Bristow Group stockholders’ investment	963,173		1,170,891
Total stockholders’ investment	970,232	$ 1,120,644	1,178,144	$ 1,228,079	$ 1,245,841	$ 1,289,283
Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued wages, benefits and related taxes	47,011		62,385
Retained earnings	615,739		793,783
Total Bristow Group stockholders’ investment	968,122		1,175,840
Total stockholders’ investment	975,181		1,183,093
Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term debt, less current maturities	(1,400,000)		(1,400,000)
Accrued wages, benefits and related taxes	4,949		4,949
Retained earnings	(4,949)		(4,949)
Total Bristow Group stockholders’ investment	(4,949)		(4,949)
Total stockholders’ investment	$ (4,949)		$ (4,949)