Accounts Notes And Loans Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts Payable Current Accounts payable Accounts Payable [Member] Accounts payable Accounts Receivable Billed For Long Term Contracts Or Programs Contracts receivable Accounts Receivable [Member] Accounts receivable-other Accounts Receivable Net Current Accounts receivable-trade, net Accrual For Environmental Loss Contingencies Environmental reserves Accrued Income Taxes Current Income taxes payable Accrued Liabilities Current Accrued liabilities Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Less accumulated depreciation Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Net loss on investments Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Net Of Tax Net gain (loss) on derivative financial instruments Net gain on derivative financial instruments Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Net Of Tax Unrecognized losses on benefit obligations Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax Foreign currency translation adjustments Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income Loss [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated other comprehensive loss Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income (Loss) Additional Paid In Capital Common Stock Capital in excess of par value Additional Paid In Capital [Member] Capital In Excess of Par Value Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Stock-based compensation charges Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Non-cash items included in net income: Allocated Share Based Compensation Expense Stock-based compensation charges Allowance For Doubtful Accounts Receivable Less allowances Amendment Flag Amendment Flag Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Antidilutive securities excluded from earnings per share computation, shares Asia Pacific [Member] Asia Pacific [Member] Asia Pacific Asset Backed Securities and Collateralized Mortgage Obligations Asset Backed Securities And Collateralized Mortgage Obligations [Member] Asset-backed securities and collateralized mortgage obligations Assets Total Assets Assets [Abstract] Assets Assets Current Total Current Assets Assets Current [Abstract] Current Assets: The aggregate value (measured at the lower of net carrying value or fair value less cost of disposal) for assets of a disposal group, including a component of the entity (discontinued operation), to be sold or that has subsequently been disposed of through sale, as of the financial statement date. Assets Held For Sale Assets, discontinued operations Assets Held For Sale Long Lived Assets Held for Sale Total long-term assets held for sale Assets held for sale, long-term assets Assets Held For Sale Other Noncurrent Other assets Assets Held For Sale Property Plant And Equipment Property, plant and equipment-net Atlantic [Member] Atlantic [Member] Atlantic Available For Sale Securities Investments, carrying amount Availableforsale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses 2 Twelve months or greater unrealized losses Available For Sale Securities Continuous Unrealized Loss Position Fair Value Table [Text Block] Available-for-Sale Securities with Unrealized Losses Greater Than Twelve Months Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value Twelve months or greater fair value Available For Sale Securities Current Investments Available For Sale Securities Fair Value Disclosure Available-for-sale securities Investments, fair value Available For Sale Securities Noncurrent Investments Available For Sale Securities [Text Block] Available-For-Sale Securities Measured at Fair Value Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Basis Of Accounting Policy Policy [Text Block] Basis of Presentation Billings In Excess Of Cost Advance billings on contracts B R Brazil Capital Expenditures Incurred But Not Yet Paid Accrued capital expenditures Cash And Cash Equivalents At Carrying Value Cash and cash equivalents Cash And Cash Equivalents Fair Value Disclosure Cash and cash equivalents, fair value Cash and Cash Equivalents of Continuing Operations, at Carrying Value. Cash And Cash Equivalents Of Continuing Operations At Carrying Value Cash and cash equivalents at end of period-Continuing Operations Cash and cash equivalents at beginning of period Cash And Cash Equivalents Period Increase Decrease Net increase in cash and cash equivalents Cash And Cash Equivalents Policy [Text Block] Cash and Cash Equivalents Cash Paid During Period For [Abstract] Cash Paid During Period For [Abstract] Cash paid during the period for: Cash Provided By Used In Investing Activities Discontinued Operations Net Cash Provided By Investing Activities-Discontinued Operations Changes In Project Estimates Costs Changes In Project Estimates Costs changes in project estimates Commercial Paper [Member] Commercial paper Commitment Expiry, Month and Year Commitment Expiry Month And Year Trigger dates, potential liquidated damages Commitments And Contingencies Commitments and Contingencies Commitments and Contingencies Disclosure [Line Items] Commitments And Contingencies Disclosure [Line Items] Commitments and Contingencies Disclosure [Line Items] Commitments and Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Table] Commitments and Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES Commitments And Contingencies Policy [Text Block] Loss Contingencies Common Stock [Member] Common Stock Common Stock Par Or Stated Value Per Share Common stock, par value Common Stock Shares Authorized Common stock, shares authorized Common Stock Shares Issued Common stock, shares issued Common Stock Value Common stock, par value $1.00 per share, authorized 400,000,000 shares; issued 243,419,194 and 242,416,424 shares at September 30, 2012 and December 31, 2011, respectively Completed project [Member] Completed Project [Member] Completed contracts Comprehensive Income Net Of Tax Comprehensive Income (Loss) Attributable to McDermott International, Inc. Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest Less: Comprehensive Income Attributable to Noncontrolling Interests Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest Total Comprehensive Income Comprehensive Income Policy Policy [Text Block] Accumulated Other Comprehensive Loss Consolidated Entities [Member] Consolidated Entities Construction In Progress [Member] Contracts in progress Contract Receivable Retainage Total retainages Contract Receivable Retainage Due After One Year Retainages expected to be collected after one year Contract Receivable Retainage Due One Year Or Less Retainages Retainages expected to be collected within one year Corporate And Other [Member] Corporate and Other Corporate Debt Securities [Member] Corporate notes and bonds Cost Of Revenue Cost of operations Cost Of Sales [Member] Cost of operations Costs And Expenses Total costs and expenses Costs And Expenses [Abstract] Costs and Expenses: Costs In Excess Of Billings On Uncompleted Contracts Or Programs Expected To Be Collected Within One Year Contracts in progress Current Fiscal Year End Date Current Fiscal Year End Date Debt Current Notes payable and current maturities of long-term debt Deferred Income Tax Expense Benefit Provision (benefit) from deferred taxes Deferred Revenue [Member] Deferred Revenue [Member] Deferred profit recognition contracts Deferred Tax Assets Net Current Deferred income taxes Deferred Tax Liabilities Current Deferred income taxes Defined Benefit Pension Plan Liabilities Noncurrent Pension Liability Defined Benefit Plan Amortization Of Gains Losses Recognized net actuarial loss and other Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Expected Return On Plan Assets Expected return on plan assets Defined Benefit Plan Interest Cost Interest cost Defined Benefit Plan Net Periodic Benefit Cost Net periodic benefit cost Defined Benefit Plans Disclosures Defined Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans [Domain] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan Service Cost Service cost Depreciation And Amortization Depreciation and amortization Derivative Fair Value Of Derivative Asset Asset Derivatives Fair Value Derivative Fair Value Of Derivative Liability Liability Derivatives Fair Value Derivative Instrument Maturity Year Derivative Instrument Maturity Year Notional value of foreign currency forward-exchange contracts, maturity date Derivative Instruments and Hedging Activities Disclosure [Line Items] Derivative Instruments And Hedging Activities Disclosure [Line Items] Derivative Instruments and Hedging Activities Disclosure [Line Items] Derivative Instruments and Hedging Activities Disclosure [Table] Derivative Instruments And Hedging Activities Disclosure [Table] Derivative Instruments and Hedging Activities Disclosure [Table] Derivative Instruments And Hedging Activities Disclosure [Text Block] DERIVATIVE FINANCIAL INSTRUMENTS Derivative Instruments Gain Loss Reclassified From Accumulated O C I Into Income Effective Portion Net Income (loss) reclassified from AOCI into income: effective portion Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net Gain (loss) recognized in income: ineffective portion and amount excluded from effectiveness testing Derivative Instruments Gain Loss Recognized In Other Comprehensive Income Effective Portion Net Amount of gain (loss) recognized in other comprehensive income (loss) Derivative [Line Items] Derivative [Line Items] Derivative Notional Amount Notional value of outstanding derivative contracts Derivatives Policy [Text Block] Derivative Financial Instruments Derivative [Table] Derivative [Table] Designated As Hedging Instrument [Member] Derivatives Designated as Hedges Disclosure - Accumulated Other Comprehensive Loss included in Stockholders' Equity [Abstract] Disclosure Accumulated Other Comprehensive Loss Included In Stockholders Equity [Abstract] Disclosure - Accumulated Other Comprehensive Loss included in Stockholders' Equity [Abstract] Disclosure - Available-for-Sale Securities Measured at Fair Value [Abstract] Disclosure Availablefor Sale Securities Measured At Fair Value [Abstract] Disclosure - Available-for-Sale Securities Measured at Fair Value [Abstract] Disclosure - Available-for-Sale Securities with Unrealized Losses Greater Than Twelve Months [Abstract] Disclosure Availablefor Sale Securities With Unrealized Losses Greater Than Twelve Months [Abstract] Disclosure - Available-for-Sale Securities with Unrealized Losses Greater Than Twelve Months [Abstract] Disclosure Basis Of Presentation And Significant Accounting Policies Additional Information [Abstract] Disclosure Basis Of Presentation And Significant Accounting Policies Additional Information [Abstract] Disclosure Basis Of Presentation And Significant Accounting Policies Additional Information [Abstract] Disclosure - Carrying Values of Major Classes of Assets and Liabilities Held for Sale included in Condensed Consolidated Balance Sheet [Abstract] Disclosure Carrying Values Of Major Classes Of Assets And Liabilities Held For Sale Included In Condensed Consolidated Balance Sheet [Abstract] Disclosure - Carrying Values of Major Classes of Assets and Liabilities Held for Sale included in Condensed Consolidated Balance Sheet [Abstract] Disclosure - Changes in Level Three Instrument Measured on Recurring Basis [Abstract] Disclosure Changes In Level Three Instrument Measured On Recurring Basis [Abstract] Disclosure - Changes in Level Three Instrument Measured on Recurring Basis [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure - Computation of Basic and Diluted Earnings Per Common Share [Abstract] Disclosure Computation Of Basic And Diluted Earnings Per Common Share [Abstract] Disclosure - Computation of Basic and Diluted Earnings Per Common Share [Abstract] Disclosure - Contract Receivables [Abstract] Disclosure Contract Receivables [Abstract] Disclosure - Contract Receivables [Abstract] Disclosure - Derivative Financial Instruments [Abstract] Disclosure Derivative Financial Instruments [Abstract] Disclosure - Derivative Financial Instruments [Abstract] Disclosure Derivative Financial Instruments Additional Information [Abstract] Disclosure Derivative Financial Instruments Additional Information [Abstract] Disclosure Derivative Financial Instruments Additional Information [Abstract] Disclosure - Dispositions - Additional Information [Abstract] Disclosure Dispositions Additional Information [Abstract] Disclosure - Dispositions - Additional Information [Abstract] Disclosure - Effects of Derivative Instruments on Financial Statements [Abstract] Disclosure Effects Of Derivative Instruments On Financial Statements [Abstract] Disclosure - Effects of Derivative Instruments on Financial Statements [Abstract] Disclosure - Estimated Fair Values of Financial Instruments [Abstract] Disclosure Estimated Fair Values Of Financial Instruments [Abstract] Disclosure - Estimated Fair Values of Financial Instruments [Abstract] Disclosure Fair Value Measurements Additional Information [Abstract] Disclosure Fair Value Measurements Additional Information [Abstract] Disclosure Fair Value Measurements Additional Information [Abstract] Disclosure - Net Periodic Benefit Cost [Abstract] Disclosure Net Periodic Benefit Cost [Abstract] Disclosure - Net Periodic Benefit Cost [Abstract] Disclosure Of Compensation Related Costs Share Based Payments [Text Block] STOCK-BASED COMPENSATION Disclosure Of Long Lived Assets Held For Sale [Text Block] Carrying Values of Major Classes of Assets and Liabilities Held for Sale included in Condensed Consolidated Balance Sheet Disclosure - Retainages on Contracts [Abstract] Disclosure Retainages On Contracts [Abstract] Disclosure - Retainages on Contracts [Abstract] Disclosure Segment Reporting Additional Information [Abstract] Disclosure Segment Reporting Additional Information [Abstract] Disclosure Segment Reporting Additional Information [Abstract] Disclosure - Selected Financial Information Regarding Results of Operations of Charter Fleet Business [Abstract] Disclosure Selected Financial Information Regarding Results Of Operations Of Charter Fleet Business [Abstract] Disclosure - Selected Financial Information Regarding Results of Operations of Charter Fleet Business [Abstract] Disclosure - Summarized Financial Information of Segments [Abstract] Disclosure Summarized Financial Information Of Segments [Abstract] Disclosure - Summarized Financial Information of Segments [Abstract] Disclosure - Total Stock-Based Compensation Expense Recognized [Abstract] Disclosure Total Stock Based Compensation Expense Recognized [Abstract] Disclosure - Total Stock-Based Compensation Expense Recognized [Abstract] Discontinued Operation Gain Loss From Disposal Of Discontinued Operation Before Income Tax Gain on disposal of discontinued operations Discontinued Operation Income Loss From Discontinued Operation During Phase Out Period Before Income Tax Income before provision for income taxes Discontinued Operation Income Loss From Discontinued Operation During Phase Out Period Net Of Tax Income from discontinued operations, net of tax Discontinued Operation Tax Effect Of Discontinued Operation Provision for income taxes Disposal Group Including Discontinued Operation Revenue Revenues Disposal Groups Including Discontinued Operations Disclosure [Text Block] DISPOSITIONS Distributions To Noncontrolling Interest Distributions To Noncontrolling Interest Distributions to noncontrolling interests Document Documentand Entity Information [Abstract] Document Documentand Entity Information [Abstract] Document Documentand Entity Information [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Document Period End Date Document Period End Date Document Type Document Type Domestic Defined Benefit Plan [Member] Domestic Defined Benefit Plan [Member] Domestic Plan Drydock [Member] Drydock [Member] Drydock Earnings Per Share [Abstract] Earnings per Common Share: Earnings Per Share Basic Net income attributable to McDermott International, Inc. Net income attributable to McDermott International, Inc. Earnings Per Share Basic [Abstract] Basic earnings per share: Basic: Earnings Per Share Diluted Net income attributable to McDermott International, Inc. Net income attributable to McDermott International, Inc. Earnings Per Share Diluted [Abstract] Diluted earnings per share: Diluted: Earnings Per Share Disclosure [Line Items] Earnings Per Share Disclosure [Line Items] Earnings Per Share Disclosure [Line Items] Earnings Per Share Disclosure [Table] Earnings Per Share Disclosure [Table] Earnings Per Share Disclosure [Table] Earnings Per Share Policy [Text Block] Earnings per Share Earnings Per Share [Text Block] EARNINGS PER SHARE Effect Of Exchange Rate On Cash And Cash Equivalents Continuing Operations Effects of exchange rate changes on cash and cash equivalents Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Employee Service Share Based Compensation Allocation Of Recognized Period Costs Report Line [Domain] Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Report Line [Domain] Entity Central Index Key Entity Central Index Key Entity Common Stock Shares Outstanding Entity Common Stock, Shares Outstanding Entity [Domain] Entity [Domain] Entity Filer Category Entity Filer Category Entity Registrant Name Entity Registrant Name Environmental Costs Recognized Recovery Credited To Expense Environmental costs recognized, recovery credited to expense Equity Component [Domain] Equity Component [Domain] Equity Method Investment Ownership Percentage Equity method of accounting investment ownership Equity Method Investments Policy Investments in Unconsolidated Affiliates Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Text Block] Changes in Level Three Instrument Measured on Recurring Basis Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value By Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value By Balance Sheet Grouping [Text Block] Estimated Fair Values of Financial Instruments Fair Value By Fair Value Hierarchy Level [Axis] Fair Value, Hierarchy [Axis] Fair Value Disclosures [Text Block] FAIR VALUE MEASUREMENTS Fair Value Inputs Level 2 [Member] Level 2 Fair Value Inputs Level 3 [Member] Level 3 Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Measurements [Line Items] Fair Value Measurements [Line Items] Fair Value Measurements [Line Items] Fair Value Measurements [Table] Fair Value Measurements [Table] Fair Value Measurements [Table] Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings 1 Total realized and unrealized gains (losses) Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Settlements Principal repayments Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value Balance at end of period Balance at beginning of period Fair Value Of Financial Instruments Policy Fair Value of Financial Instruments Financing Receivable, by Contractual Maturity. Financing Receivable By Contractual Maturity [Text Block] Retainages on Contracts Finite Lived Intangible Assets By Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite Lived Intangible Assets Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Foreign Currency Cash Flow Hedge Gain Loss To Be Reclassified During Next 12 Months Net deferred gains expected to be reclassified out of AOCI over the next 12 months Foreign Currency Contract Asset Fair Value Disclosure Fair value of foreign currency forward-exchange contracts in net asset position Foreign Currency Gain Loss [Member] Gain (loss) on foreign currency - net Foreign Currency Transaction Gain Loss Before Tax Gain (loss) on foreign currency - net Foreign Currency Transactions And Translations Policy [Text Block] Foreign Currency Translation Forward contracts Assets (Liabilities) At Carrying Value Forward Contracts Assets Liabilities At Carrying Value Forward contracts, carrying amount Forward contracts Assets (Liabilities), at Fair Value Forward Contracts Assets Liabilities At Fair Value Forward contracts, fair value Gain Loss On Disposition Of Assets Gain on asset disposals Gain Loss On Sales Of Assets And Asset Impairment Charges Gain on asset disposals and impairments-net Goodwill Goodwill Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Impairment of Long Lived Assets, Intangible Assets and Equity Investments Policy. Impairment Of Long Lived Assets Intangible Assets And Equity Investments Policy [Text Block] Impairment Review Income Loss From Continuing Operations Income from continuing operations less noncontrolling interests Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments Income from continuing operations before provision for income taxes and noncontrolling interests Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest Income from continuing operations Income from continuing operations before noncontrolling interests Income Loss From Continuing Operations Per Basic Share Income from continuing operations less noncontrolling interests Income from continuing operations, less noncontrolling interests Income Loss From Continuing Operations Per Diluted Share Income from continuing operations less noncontrolling interests Income from continuing operations, less noncontrolling interests Income Loss From Discontinued Operations Net Of Tax Income from discontinued operations, net of tax Total income from discontinued operations, net of tax Less: Income from discontinued operations, net of tax Income Loss From Discontinued Operations Net Of Tax Per Basic Share Income from discontinued operations, net of tax Income Loss From Discontinued Operations Net Of Tax Per Diluted Share Income from discontinued operations, net of tax Income Loss From Equity Method Investments Equity in Income (Loss) of Unconsolidated Affiliates Equity in (income) loss of unconsolidated affiliates Income Statement [Abstract] Income Statement [Abstract] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Table] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Income Taxes Paid Net Income taxes (net of refunds) Income Tax Expense Benefit Provision for Income Taxes Increase Decrease In Accounts Payable Accounts payable Increase Decrease In Accounts Receivable Accounts receivable Changes in contracts in progress and advance billings, net. Increase Decrease In Contracts In Progress And Advance Billings Contracts Net contracts in progress and advance billings on contracts Increase Decrease In Operating Capital [Abstract] Changes in assets and liabilities, net of effects from dispositions: Increase Decrease In Other Accrued Liabilities Accrued and other current liabilities Increase Decrease In Other Operating Capital Net Other assets and liabilities Change in accrued employee benefits, retirement reserve and accumulated postretirement benefits, net. Increase Decrease In Pension Liability And Accrued Postretirement And Employee Benefits Pension liability and accrued postretirement and employee benefits Increase Decrease In Restricted Cash (Increase) decrease in restricted cash and cash equivalents Interest Expense Interest expense Investment Income Interest Interest income Investment Policy [Text Block] Investments Investments In Affiliates Subsidiaries Associates And Joint Ventures Investments in Unconsolidated Affiliates Legal Claim 3 [Member] Legal Claim Three [Member] Antoine, et al. vs. J. Ray McDermott, Inc., et al. Legal Claim 2 [Member] Legal Claim Two [Member] Boudreaux, et al. v. McDermott, Inc., et al. Legal Entity [Axis] Legal Entity [Axis] Liabilities And Stockholders Equity Total Liabilities and Equity Liabilities And Stockholders Equity [Abstract] Liabilities and Equity Liabilities Current Total Current Liabilities Liabilities Current [Abstract] Current Liabilities: Litigation Case [Axis] Litigation Case [Axis] Litigation Case Type [Domain] Litigation Case Type [Domain] Long Term Debt Debt, carrying amount Long Term Debt And Capital Lease Obligations Long-Term Debt Long Term Debt Fair Value Debt, fair value Loss Contingencies By Nature Of Contingency [Axis] Loss Contingency Nature [Axis] Loss Contingency Accrual At Carrying Value Liquidated damage contingencies, accrued Loss Contingency Dismissal Description Loss Contingency Dismissal Description Legal claims Loss Contingency Estimate Of Possible Loss Aggregate possible liquidated damage due to failure to meet specified contractual milestone dates, offshore oil and gas construction segment Loss Contingency Nature [Domain] Loss Contingency, Nature [Domain] Loss Contingency Number Of Defendants Number of defendants Loss Contingency Number Of Plaintiffs Number of plaintiffs Major Property Class [Axis] Major Property Class [Axis] Major Property Class [Domain] Major Property Class [Domain] Major Types Of Debt And Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types Of Debt And Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Marine Charter Fleet [Member] Marine Charter Fleet [Member] Charter Fleet Business Maximum [Member] Maximum Middle East [Member] Middle East [Member] Middle East Minimum [Member] Minimum Minority Interest Noncontrolling Interests Minority Interest Decrease From Distributions To Noncontrolling Interest Holders Distributions to noncontrolling interests Multi Purpose Support Vessel [Member] Multi Purpose Support Vessel [Member] Multi Function Support Vessel Mutual Funds [Member] Mutual Funds [Member] Mutual funds M X Mexico Nature of Operations. Nature Of Operations Policy [Text Block] Nature of Operations Net Cash Provided By Used In Financing Activities Continuing Operations Net Cash Provided By (Used In) Financing Activities-Continuing Operations Net Cash Provided By Used In Financing Activities Continuing Operations [Abstract] Cash Flows From Financing Activities: Net Cash Provided By Used In Investing Activities Total Cash Provided By (Used In) Investing Activities Net Cash Provided By Used In Investing Activities Continuing Operations Net Cash Provided By (Used In) Investing Activities-Continuing Operations Net Cash Provided By Used In Investing Activities Continuing Operations [Abstract] Cash Flows From Investing Activities: Net Cash Provided By Used In Operating Activities Total Cash Provided By (Used In) Operating Activities Net Cash Provided By Used In Operating Activities Continuing Operations Net Cash Provided By (Used In) Operating Activities-Continuing Operations Net Cash Provided By Used In Operating Activities Continuing Operations [Abstract] Cash Flows From Operating Activities: Net Cash Provided by (Used in) Operating Activities, Discontinued Operations Net Cash Provided By Used In Operating Activities Discontinued Operations Net Cash Used In Operating Activities-Discontinued Operations Net Income Loss Net income attributable to McDermott International, Inc. Net Income Loss Attributable To Noncontrolling Interest Less: Net Income Attributable to Noncontrolling Interests New Accounting Pronouncements Policy Policy [Text Block] Recently Issued Accounting Standards Noncontrolling Interest [Member] Non- Controlling Interests Nonoperating Income Expense Total other income (expense) Nonoperating Income Expense [Abstract] Other Income (Expense): Notional Amount Of Foreign Currency Cash Flow Hedge Derivatives Notional value of foreign currency forward-exchange contracts Number Of Operating Segments Number of primary operating segments Number of Projects Number Of Projects Number of projects accounted under deferred profit recognition policy Number Of Reportable Segments Number of reporting segments Number of Vessels Number Of Vessels Number of vessels Number of Vessels Held for Sale Number Of Vessels Held For Sale Number of vessels held for sale Number of Vessels Sold Number Of Vessels Sold Number of vessels Operating Income Loss Operating income (loss) Operating Income Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] Organization, Consolidation and Presentation of Financial Statements Disclosure [Table] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Organization, Consolidation and Presentation of Financial Statements Disclosure [Table] Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Other Assets Current Other current assets Other Assets Held For Sale Assets held for sale Other Assets Held For Sale Current Assets held for sale, other current assets Other current assets Other Assets [Member] Other assets Other Assets Noncurrent Other Assets Other Comprehensive Income Loss Amortization Pension And Other Postretirement Benefit Plans Net Prior Service Cost Recognized In Net Periodic Pension Cost Net Of Tax Amortization of benefit plan costs Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax Unrealized gain (loss) on derivatives Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax Translation adjustments Other Comprehensive Income Loss Net Of Tax Other comprehensive income, net of tax Other comprehensive income (loss), net of tax Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Other comprehensive income (loss), net of tax: Represents the change in net unrealized gains (losses) on securities during the period, excluding the non-credit portion of other-than-temporary impairment losses, net of tax Other Comprehensive Income Loss Net Unrealized Gains Losses On Securities Net Of Tax Period Increase Decrease Unrealized gain (loss) on investments Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax Unrealized gain on benefit plan revaluation Other Comprehensive Income Loss Reclassification Adjustment For Sale Of Securities Included In Net Income Net Of Tax Realized loss on investments Other Comprehensive Income Loss Reclassification Adjustment On Derivatives Included In Net Income Net Of Tax Realized (gain) loss on derivatives Other Employer [Member] Other Employer [Member] Other Employers than JRMI and MI Other Liabilities [Member] Other liabilities Other Liabilities Noncurrent Other Liabilities Other Noncash Income Expense Other non-cash items Other Nonoperating Income Expense Other income (expense) - net Other products [Member] Other Products [Member] Maritime products Other Receivables Net Current Accounts receivable - other Accounts receivable-other Parent [Member] Stockholders' Equity Payments For Proceeds From Other Investing Activities Other investing activities, net Payments For Proceeds From Productive Assets Proceeds from asset disposals Payments Of Debt Issuance Costs Debt issuance costs Payments To Acquire Available For Sale Securities Purchases of available-for-sale securities Payments To Acquire Property Plant And Equipment Capital expenditures Purchases of property, plant and equipment Pension And Other Postretirement Benefits Disclosure [Text Block] PENSION PLANS Pension Expense Pension costs Percentage of completion Percentage Of Completion Percentage of completion to recognize expected profit Performance and Deferred Stock Units [Member] Performance And Deferred Stock Units [Member] Performance Shares and Deferred Stock Units Proceeds From Divestiture Of Businesses Proceeds from sale of business Proceeds From Issuance Of Long Term Debt Increase in debt Proceeds From Payments For Other Financing Activities Other financing activities, net Proceeds From Sale And Maturity Of Available For Sale Securities Sales and maturities of available-for-sale securities Profit Loss Net income Net Income Property Plant And Equipment By Type [Axis] Property, Plant and Equipment, Type [Axis] Property Plant And Equipment Gross Property, Plant and Equipment Property Plant And Equipment Net Net Property, Plant and Equipment Property Plant And Equipment Type [Domain] Property, Plant and Equipment, Type [Domain] Range [Axis] Range [Axis] Range [Member] Range [Domain] Receivables Policy [Text Block] Accounts Receivable Repayments Of Debt Payment of debt Restricted Cash And Cash Equivalents At Carrying Value Restricted cash and cash equivalents, carrying amount Restricted cash and cash equivalents Restricted cash and cash equivalents, aggregate amount Restricted Cash and Cash Equivalents, Fair Value Disclosure Restricted Cash And Cash Equivalents Fair Value Disclosure Restricted cash and cash equivalents, fair value Restricted Stock Units And Restricted Stock [Member] Restricted Stock Units And Restricted Stock [Member] Restricted Stock and Restricted Stock Units Retained Earnings Accumulated Deficit Retained earnings Retained Earnings [Member] Retained Earnings Revenue Recognition Policy [Text Block] Revenue Recognition Revenues Revenues Scenario Unspecified [Domain] Scenario, Unspecified [Domain] Schedule Of Accounts Notes Loans And Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule Of Accounts Notes Loans And Financing Receivable [Text Block] Contracts Receivables Schedule Of Accumulated Other Comprehensive Income Loss Table [Text Block] Accumulated Other Comprehensive Loss included in Stockholders' Equity Schedule Of Available For Sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Schedule Of Available For Sale Securities [Table] Schedule of Available-for-sale Securities [Table] Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share Table [Text Block] Computation of Basic and Diluted Earnings Per Common Share Schedule Of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Schedule Of Defined Benefit Plans Disclosures [Text Block] Net Periodic Benefit Cost Schedule Of Derivative Instruments Gain Loss In Statement Of Financial Performance [Text Block] Effects of Derivative Instruments on Financial Statements Schedule Of Derivative Instruments In Statement Of Financial Position Fair Value [Text Block] Derivative Financial Instruments Schedule of Discontinued Operations, Income Statement Disclosures. Schedule Of Discontinued Operations Income Statement Disclosures [Text Block] Selected Financial Information Regarding Results of Operations of Charter Fleet Business Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs By Report Line [Axis] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs, by Report Line [Axis] Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Total Stock-Based Compensation Expense Recognized Schedule Of Segment Reporting Information By Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Schedule Of Segment Reporting Information By Segment [Text Block] Summarized Financial Information of Segments Secunda International Limited [Member] Secunda International Limited [Member] Secunda International Limited Securities, Maturity Securities Maturity Available-for-sale securities, maturities Segment [Domain] Segment [Domain] Segment Geographical [Domain] Segment, Geographical [Domain] Segment Geographical Region [Domain] Segment Geographical Region [Domain] Segment Geographical Region [Domain] Segment Reporting Disclosure [Text Block] SEGMENT REPORTING Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Segment Reporting Policy Policy [Text Block] Business Segments Self Insurance Reserve Noncurrent Self-Insurance Selling General And Administrative Expense Selling, general and administrative expenses Share Based Compensation Stock-based compensation expenses Shares Issued Ending balance (in shares) Beginning balance (in shares) Statement Business Segments [Axis] Business Segments [Axis] Statement Equity Components [Axis] Equity Components [Axis] Statement Geographical [Axis] Geographical [Axis] Statement Geographical Region [Axis] Statement Geographical Region [Axis] Statement Geographical Region [Axis] Statement [Line Items] Statement [Line Items] Statement Of Cash Flows [Abstract] CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Statement Of Financial Position [Abstract] CONDENSED CONSOLIDATED BALANCE SHEETS Statement Of Income And Comprehensive Income [Abstract] Statement of Other Comprehensive Income [Abstract] Statement Of Stockholders Equity [Abstract] CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement Scenario [Axis] Scenario [Axis] Statement [Table] Statement [Table] Stockholders Equity Stockholders' Equity-McDermott International, Inc. Stockholders Equity Including Portion Attributable To Noncontrolling Interest Ending balance Beginning balance Total Equity Stockholders Equity Including Portion Attributable To Noncontrolling Interest [Abstract] Stockholders' Equity: Stock Issued During Period Shares Stock Options Exercised Exercise of stock options (in shares) Stock Issued During Period Value Stock Options Exercised Exercise of stock options Number of common stock issued as a result of granting or vesting of employee stock awards (including income tax benefits), and the shares of treasury stock purchases related to withholding taxes. Stock Issued Or Vested During Period Shares Stock Awards Share vesting (in shares) Total value of common stock issued as a result of granting or vesting of employee stock awards (including income tax benefits), and the value of treasury stock purchases related to withholding taxes. Stock Issued Or Vested During Period Value Stock Awards Share vesting Stock Options [Member] Stock Options Supplemental Cash Flow Information [Abstract] Supplemental Disclosures of Cash Flow Information: Text Block [Abstract] Text Block [Abstract] TCN Plan [Member] Third Country National Employees Pension Plan [Member] TCN Plan Total Assets, Continuing Operations Total Assets Continuing Operations Assets, continuing operations Trading Symbol Trading Symbol Treasury Stock [Member] Treasury Stock Treasury Stock Shares Treasury stock, shares Treasury Stock Value Treasury stock, at cost, 7,574,903 and 7,359,983 shares at September 30, 2012 and December 31, 2011, respectively Treasury Stock Value Acquired Cost Method Purchase of treasury shares Unbilled Contracts Receivable Unbilled Unconsolidated Affiliates [Member] Unconsolidated Affiliates [Member] Unconsolidated joint ventures US State District Court [Member] United States State District Court [Member] United States District Court for the Southern District of Texas US State District Court 1 [Member] United States State District Court One [Member] Judicial District Court for Harris County, Texas Use Of Estimates Use of Estimates Vessels [Member] Vessels [Member] DB 23marine vessel Weighted Average Number Diluted Shares Outstanding Adjustment Stock options, restricted stock and restricted stock units Weighted Average Number Diluted Shares Outstanding Adjustment [Abstract] Effect of dilutive securities: Weighted Average Number Of Diluted Shares Outstanding Diluted Adjusted weighted average common shares and assumed exercises of stock options and vesting of stock awards (diluted) Weighted Average Number Of Shares Outstanding [Abstract] Shares used in the computation of earnings per share: Weighted Average Number Of Shares Outstanding Basic Basic Weighted average common shares (basic)