VARIABLE INTEREST ENTITIES - Balance Sheets of VIEs (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
Variable Interest Entity [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
Prepaid expenses and other current assets	46,603	47,234
Total current assets	728,097	834,399
Investment in unconsolidated affiliates	110,637	126,170
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
Accrued interest	17,154	16,345
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
Accrued pension liabilities	28,484	37,034
Other liabilities and deferred credits	31,639	36,952
Deferred taxes	97,372	115,192
Bristow Aviation Holdings Limited
Variable Interest Entity [Line Items]
Cash and cash equivalents	69,468	90,788
Accounts receivable	310,999	256,735
Inventories	81,069	98,314
Prepaid expenses and other current assets	38,594	38,665
Total current assets	500,130	484,502
Investment in unconsolidated affiliates	3,113	3,608
Property and equipment, net	287,817	327,440
Goodwill	18,778	19,907
Other assets	226,612	231,884
Total assets	1,036,450	1,067,341
Accounts payable	370,564	292,893
Accrued liabilities	129,011	140,733
Accrued interest	2,262,962	2,130,433
Short-term borrowings and current maturities of long-term debt	15,715	23,125
Total current liabilities	2,778,252	2,587,184
Long-term debt, less current maturities	464,322	479,571
Accrued pension liabilities	28,484	37,034
Other liabilities and deferred credits	7,231	7,342
Deferred taxes	28,157	26,252
Liabilities	$ 3,306,446	$ 3,137,383