Reclassifications from Accumulated Other Comprehensive Income (Loss) to Condensed Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net	$ 992	$ 355	$ 2,168	$ 1,145
Interest and other debt costs	18,477	13,247	35,431	26,429
Loss before income taxes	(174,055)	(32,611)	(258,702)	(37,488)
Tax effect	3,568	11,388	7,564	21,675
Net loss attributable to Tidewater Inc.	(178,490)	(43,835)	(267,587)	(58,887)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss before income taxes	112	374	285	744
Tax effect		131		260
Net loss attributable to Tidewater Inc.	112	243	285	484
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	40	97	142	192
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	$ 72	$ 277	$ 143	$ 552