Employee Retirement Plans - Additional Information (Detail)		1 Months Ended	4 Months Ended	5 Months Ended	9 Months Ended	12 Months Ended
	Dec. 01, 2015	Apr. 30, 2018 USD ($)	Jul. 31, 2017 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) Person shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 shares	Aug. 01, 2017 shares
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, concentration risk, assets, equity securities, difference plan assets and liabilities							15.00%
Defined benefit plan, concentration risk, assets, equity securities, maximum foreign and us stock							10.00%
Defined benefit plan, significant concentrations of risk							The pension plan assets are periodically evaluated for concentration risks. As of December 31, 2019, we did not have any individual asset investments that comprised 10% or more of each plan’s overall assets.
Unrecognized actuarial (loss) gain							$ 0
Unrecognized prior service credit (cost)							$ 0
Discount rates							3.50%	4.50%
Defined contribution plan, description							Effective January 1, 2018, we no longer provide a matching of 50% of the first 8% of eligible compensation in an attempt to reduce costs.
Number of shares of Tidewater common stock held by 401(k) plan | shares			264,504
Number of shares of Tidewater Series warrants held by 401(k) plan | shares				924,125	924,125				924,125
Norways Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions					$ 300,000		$ 700,000	$ 200,000
Number of employers still remains in defined benefit plan | Person							100
Norways Defined Benefit Pension Plan | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions						$ 500,000
Retirement Contributions
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, company contribution percentage							3.00%
Defined contribution plan, company contribution, vesting period, years							5 years
Defined Contribution Savings Plan 401k
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, company contribution, vesting period, years							5 years
Percentage of defined plan, minimum employee contribution							2.00%
Percentage of defined plan, maximum employee contribution							75.00%
Percentage of defined plan, company contribution match, cash									50.00%
Percentage of defined plan, company contribution match, employee deferred compensation							8.00%		8.00%
Defined contribution plan, company contribution percentage match, company stock							50.00%
Number of shares of Tidewater common stock held by 401(k) plan | shares				8,074	8,074		0	7,075	8,074
Defined Contribution Plan Expense			$ 900,000	$ 900,000
Defined Contribution Savings Plan 401k | Series A Warrants
Defined Benefit Plan Disclosure [Line Items]
Number of shares of Tidewater Series warrants held by 401(k) plan | shares										9,030
Defined Contribution Savings Plan 401k | Series B Warrents
Defined Benefit Plan Disclosure [Line Items]
Number of shares of Tidewater Series warrants held by 401(k) plan | shares				9,762	9,762				9,762
Non-Qualified Supplemental Savings Plan Executives
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, company contribution percentage match, common stock								50.00%
Deferred compensation arrangement with individual, deferred compensation percentage								50.00%
Deferred compensation arrangement with individual, deferred bonus percentage								100.00%
Defined contribution plan, restoration benefit							3.00%
Multinational Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, company contribution, vesting period, years	5 years
Percentage of defined plan, minimum employee contribution	1.00%
Percentage of defined plan, maximum employee contribution	50.00%
Percentage of defined plan, company contribution match, cash	50.00%
Percentage of defined plan, company contribution match, employee deferred compensation	6.00%
Merchant Navy Officers Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Multi-employer retirement fund liability							$ 1,000,000.0	$ 1,400,000
Multi-employer retirement fund expense							200,000
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions					$ 0		1,100,000	0
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions					$ 100,000		3,200,000	900,000
Supplemental Executive Retirement Plan | President, and Chief Executive Officer
Defined Benefit Plan Disclosure [Line Items]
Settlement of distribution		$ 8,900,000
Settlement loss		$ (300,000)
Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Gain on termination of post retirement benefit plan								$ 4,000,000.0
Postretirement benefit plan obligations reduction							$ 1,900,000