Reclassifications from Accumulated Other Comprehensive Income (Loss) to Condensed Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net	$ 1,680	$ 1,176
Interest and other debt costs	10,605	16,954
Loss before income taxes	(524,115)	(84,647)
Tax effect	295	3,996
Net loss attributable to Tidewater Inc.	(524,434)	(89,097)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss before income taxes	80	173
Net loss attributable to Tidewater Inc.	80	173
Reclassification out of Accumulated Other Comprehensive Income | Available for Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net	$ 80	102
Reclassification out of Accumulated Other Comprehensive Income | Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and other debt costs		$ 71