Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Interest and debt related expenses associated with nonoperating financing activities of the entity.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Reclassifications from Accumulated Other Comprehensive Income (Loss) to Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	1 Months Ended	2 Months Ended	3 Months Ended						4 Months Ended	5 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2017	Sep. 30, 2017	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net										$ 2,771
Interest and other debt costs										13,009
Loss before income taxes										(36,687)
Tax effect										2,039
Net loss attributable to Tidewater Inc.		$ (15,693)	$ (23,573)							(39,266)
Predecessor
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net									$ 2,384			$ 5,193
Interest and other debt costs									11,179			75,026
Loss before income taxes									(1,648,143)		$ (558,359)	(643,614)
Tax effect									(1,234)		4,680	6,397
Net loss attributable to Tidewater Inc.	$ (1,122,475)			$ (524,434)	$ (94,855)	$ (297,676)	$ (178,490)	$ (89,097)	(1,646,909)		$ (565,263)	(660,118)
Reclassification out of Accumulated Other Comprehensive Income \| Predecessor
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss before income taxes									106	169		2,935
Tax effect												1,027
Net loss attributable to Tidewater Inc.									106	169		1,908
Reclassification out of Accumulated Other Comprehensive Income \| Predecessor \| Available for Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income and other, net									$ 106	$ 169		582
Reclassification out of Accumulated Other Comprehensive Income \| Predecessor \| Interest Rate Swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and other debt costs												$ 2,353