<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Version>2.4.0.6</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>281</ContextCount>
  <ElementCount>368</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>72</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>10</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Consolidated Statements of Financial Condition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfFinancialCondition</Role>
      <ShortName>Consolidated Statements of Financial Condition</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Consolidated Statements of Financial Condition (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfFinancialConditionParenthetical</Role>
      <ShortName>Consolidated Statements of Financial Condition (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Consolidated Statements of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>Consolidated Statements of Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Statements of Changes in Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfChangesInEquity</Role>
      <ShortName>Consolidated Statements of Changes in Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004501 - Statement - Consolidated Statements of Changes in Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfChangesInEquityParenthetical</Role>
      <ShortName>Consolidated Statements of Changes in Equity (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005000 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Organization</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/Organization</Role>
      <ShortName>Organization</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Acquisition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/Acquisition</Role>
      <ShortName>Acquisition</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/Investments</Role>
      <ShortName>Investments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Goodwill</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/Goodwill</Role>
      <ShortName>Goodwill</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Related Parties</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RelatedParties</Role>
      <ShortName>Related Parties</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Property and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/PropertyAndEquipment</Role>
      <ShortName>Property and Equipment</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Revolving Bank Loan Facility</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RevolvingBankLoanFacility</Role>
      <ShortName>Revolving Bank Loan Facility</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/Equity</Role>
      <ShortName>Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Retirement Plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RetirementPlan</Role>
      <ShortName>Retirement Plan</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Restricted Stock Units</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RestrictedStockUnits</Role>
      <ShortName>Restricted Stock Units</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Regulatory Requirements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RegulatoryRequirements</Role>
      <ShortName>Regulatory Requirements</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Business Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/BusinessInformation</Role>
      <ShortName>Business Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - Supplemental Financial Information Quarterly Results</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SupplementalFinancialInformationQuarterlyResults</Role>
      <ShortName>Supplemental Financial Information Quarterly Results</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2202201 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Acquisition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/AcquisitionTables</Role>
      <ShortName>Acquisition (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Goodwill (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/GoodwillTables</Role>
      <ShortName>Goodwill (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Property and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/PropertyAndEquipmentTables</Role>
      <ShortName>Property and Equipment (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Restricted Stock Units (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RestrictedStockUnitsTables</Role>
      <ShortName>Restricted Stock Units (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - Business Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/BusinessInformationTables</Role>
      <ShortName>Business Information (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2318301 - Disclosure - Supplemental Financial Information Quarterly Results (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SupplementalFinancialInformationQuarterlyResultsTables</Role>
      <ShortName>Supplemental Financial Information Quarterly Results (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Acquisition - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/AcquisitionAdditionalInformationDetail</Role>
      <ShortName>Acquisition - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Acquisition - Assets Acquired and Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/AcquisitionAssetsAcquiredAndLiabilitiesAssumedDetails</Role>
      <ShortName>Acquisition - Assets Acquired and Liabilities Assumed (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2403404 - Disclosure - Acquisition - Unaudited Pro Forma Results of Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/AcquisitionUnauditedProFormaResultsOfOperationsDetails</Role>
      <ShortName>Acquisition - Unaudited Pro Forma Results of Operations (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Investments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsAdditionalInformationDetail</Role>
      <ShortName>Investments - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Investments - Carrying Value of Investments in Merchant Banking Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsCarryingValueOfInvestmentsInMerchantBankingFundsDetails</Role>
      <ShortName>Investments - Carrying Value of Investments in Merchant Banking Funds (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Investments - Other Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsOtherInvestmentsDetails</Role>
      <ShortName>Investments - Other Investments (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Investments - Investment Revenues (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsInvestmentRevenuesDetails</Role>
      <ShortName>Investments - Investment Revenues (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Investments - Assets Measured at Fair Value on Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsAssetsMeasuredAtFairValueOnRecurringBasisDetails</Role>
      <ShortName>Investments - Assets Measured at Fair Value on Recurring Basis (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2404407 - Disclosure - Investments - Changes In Fair Value of Level 3 Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/InvestmentsChangesInFairValueOfLevel3InvestmentsDetails</Role>
      <ShortName>Investments - Changes In Fair Value of Level 3 Investments (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Goodwill - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/GoodwillAdditionalInformationDetail</Role>
      <ShortName>Goodwill - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - Goodwill Goodwill - Changes in Carrying Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/GoodwillGoodwillChangesInCarryingValueDetails</Role>
      <ShortName>Goodwill Goodwill - Changes in Carrying Value (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2406401 - Disclosure - Related Parties - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RelatedPartiesAdditionalInformationDetail</Role>
      <ShortName>Related Parties - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Property and Equipment - Components of Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/PropertyAndEquipmentComponentsOfPropertyAndEquipmentDetails</Role>
      <ShortName>Property and Equipment - Components of Property and Equipment (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2408401 - Disclosure - Revolving Bank Loan Facility - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RevolvingBankLoanFacilityAdditionalInformationDetail</Role>
      <ShortName>Revolving Bank Loan Facility - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2409401 - Disclosure - Equity - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/EquityAdditionalInformationDetail</Role>
      <ShortName>Equity - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Earnings Per Share - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/EarningsPerShareAdditionalInformationDetails</Role>
      <ShortName>Earnings Per Share - Additional Information (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Earnings Per Share Earnings Per Share - Reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/EarningsPerShareEarningsPerShareReconciliationDetails</Role>
      <ShortName>Earnings Per Share Earnings Per Share - Reconciliation (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2411401 - Disclosure - Retirement Plan - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RetirementPlanAdditionalInformationDetail</Role>
      <ShortName>Retirement Plan - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Restricted Stock Units - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RestrictedStockUnitsAdditionalInformationDetail</Role>
      <ShortName>Restricted Stock Units - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2412403 - Disclosure - Restricted Stock Units - Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RestrictedStockUnitsActivityDetail</Role>
      <ShortName>Restricted Stock Units - Activity (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/CommitmentsAndContingenciesAdditionalInformationDetail</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/CommitmentsAndContingenciesApproximateAggregateMinimumFutureRentalPaymentsRequiredDetails</Role>
      <ShortName>Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/CommitmentsAndContingenciesApproximateAggregateMinimumFutureRentalPaymentsRequiredParentheticalDetails</Role>
      <ShortName>Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Parenthetical) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Income Taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/IncomeTaxesAdditionalInformationDetail</Role>
      <ShortName>Income Taxes - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Income Taxes - Provision for Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/IncomeTaxesProvisionForIncomeTaxesDetails</Role>
      <ShortName>Income Taxes - Provision for Income Taxes (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2414404 - Disclosure - Income Taxes - Net Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/IncomeTaxesNetDeferredTaxAssetsAndLiabilitiesDetails</Role>
      <ShortName>Income Taxes - Net Deferred Tax Assets and Liabilities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2414405 - Disclosure - Income Taxes - Reconciliation of Statutory U.S. Federal Income Tax Rate to Company's Effective Income Tax Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/IncomeTaxesReconciliationOfStatutoryUSFederalIncomeTaxRateToCompanysEffectiveIncomeTaxRateDetails</Role>
      <ShortName>Income Taxes - Reconciliation of Statutory U.S. Federal Income Tax Rate to Company's Effective Income Tax Rate (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2415401 - Disclosure - Regulatory Requirements - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/RegulatoryRequirementsAdditionalInformationDetail</Role>
      <ShortName>Regulatory Requirements - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - Business Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/BusinessInformationAdditionalInformationDetail</Role>
      <ShortName>Business Information - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2416403 - Disclosure - Business Information - Information by Geographic Region, After Elimination of All Significant Inter-company Accounts and Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/BusinessInformationInformationByGeographicRegionAfterEliminationOfAllSignificantInterCompanyAccountsAndTransactionsDetails</Role>
      <ShortName>Business Information - Information by Geographic Region, After Elimination of All Significant Inter-company Accounts and Transactions (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2417401 - Disclosure - Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>Subsequent Events - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2418402 - Disclosure - Supplemental Financial Information Quarterly Results Supplemental Financial Information - Schedule of Unaudited Quarterly Results (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenhill.com/role/SupplementalFinancialInformationQuarterlyResultsSupplementalFinancialInformationScheduleOfUnauditedQuarterlyResultsDetails</Role>
      <ShortName>Supplemental Financial Information Quarterly Results Supplemental Financial Information - Schedule of Unaudited Quarterly Results (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element ghl_BusinessAcquisitionPurchasePriceAllocationDeferredCompensationPlanInvestments had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element ghl_BusinessAcquisitionPurchasePriceAllocationDueToAffiliates had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element ghl_ContingentConvertiblePreferredStockValue had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element ghl_LineOfCreditFacilityWeightedAverageInterestRateDuringPeriod had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Element invest_InvestmentWarrantsExercisePrice had a mix of decimals attribute values: 0 2.</Log>
    <Log type="Info">Element us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillAmount had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_ProfessionalFees had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_RestrictedCashAndCashEquivalents had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_RestrictedStockExpense had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_ValuationAllowanceAmount had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">'Monetary' elements on report '2402402 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2403402 - Disclosure - Acquisition - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2404402 - Disclosure - Investments - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2409401 - Disclosure - Equity - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2411401 - Disclosure - Retirement Plan - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2414402 - Disclosure - Income Taxes - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Consolidated Statements of Financial Condition</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2010'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2009'</Log>
    <Log type="Info">Process Flow-Through: 1001501 - Statement - Consolidated Statements of Financial Condition (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Consolidated Statements of Income</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Consolidated Statements of Comprehensive Income</Log>
    <Log type="Info">Process Flow-Through: 1004501 - Statement - Consolidated Statements of Changes in Equity (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1005000 - Statement - Consolidated Statements of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>ghl-20121231.xml</File>
    <File>ghl-20121231.xsd</File>
    <File>ghl-20121231_cal.xml</File>
    <File>ghl-20121231_def.xml</File>
    <File>ghl-20121231_lab.xml</File>
    <File>ghl-20121231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
