Reclassifications from Accumulated Other Comprehensive Income (Loss) to Condensed Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net	$ 2,470	$ (128)
Tax effect	5,830	3,321
Net loss attributable to Tidewater Inc.	$ (21,731)	(39,172)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net loss attributable to Tidewater Inc.		361
Reclassification out of Accumulated Other Comprehensive Income | Realized Gains on Available for Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net		$ 361