<?xml version="1.0" encoding="US-ASCII"?>
<!-- DFS Xcelerate Taxonomy Schema - http://www.dfsco.com/financial-services/ -->
<!-- Version: 6.23.6 -->
<!-- Round: 3 -->
<!-- Creation date: 2017-04-28T14:41:54Z -->
<!-- Copyright (c) 2017 Donnelley Financial, LLC. All Rights Reserved. -->
<schema xmlns="http://www.w3.org/2001/XMLSchema"
  xmlns:xbrli="http://www.xbrl.org/2003/instance"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:us-gaap="http://fasb.org/us-gaap/2016-01-31"
  xmlns:us-types="http://fasb.org/us-types/2016-01-31"
  xmlns:ajg="http://www.ajg.com/20170331"
  xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric"
  xmlns:num="http://www.xbrl.org/dtr/type/numeric"
  xmlns:xbrldt="http://xbrl.org/2005/xbrldt"
  xmlns:country="http://xbrl.sec.gov/country/2016-01-31"
  xmlns:currency="http://xbrl.sec.gov/currency/2016-01-31"
  xmlns:dei="http://xbrl.sec.gov/dei/2014-01-31"
  xmlns:exch="http://xbrl.sec.gov/exch/2016-01-31"
  xmlns:invest="http://xbrl.sec.gov/invest/2013-01-31"
  xmlns:naics="http://xbrl.sec.gov/naics/2011-01-31"
  xmlns:sic="http://xbrl.sec.gov/sic/2011-01-31"
  xmlns:stpr="http://xbrl.sec.gov/stpr/2011-01-31"
  targetNamespace="http://www.ajg.com/20170331"
  elementFormDefault="qualified" attributeFormDefault="unqualified">
  <annotation>
    <appinfo>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DocumentandEntityInformation" id="DocumentandEntityInformation">
        <link:definition>101 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfIncome" id="Role_StatementOfIncome">
        <link:definition>103 - Statement - Consolidated Statement of Earnings (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfOtherComprehensiveIncome" id="Role_StatementOfOtherComprehensiveIncome">
        <link:definition>104 - Statement - Consolidated Statement of Comprehensive Earnings (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfFinancialPositionClassified" id="Role_StatementOfFinancialPositionClassified">
        <link:definition>105 - Statement - Consolidated Balance Sheet</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfFinancialPositionClassifiedParenthetical" id="Role_StatementOfFinancialPositionClassifiedParen">
        <link:definition>106 - Statement - Consolidated Balance Sheet (Parenthetical)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfCashFlowsIndirectInvestmentBasedOperations" id="Role_StatementOfCashFlowsIndirectInvestmentBasedOperations">
        <link:definition>107 - Statement - Consolidated Statement of Cash Flows (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncome" id="Role_StatementOfShareholdersEquityAndOtherComprehensiveIncome">
        <link:definition>108 - Statement - Consolidated Statement of Stockholders' Equity (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncomeParenthetical" id="Role_StatementOfShareholdersEquityAndOtherComprehensiveIncomeParen">
        <link:definition>109 - Statement - Consolidated Statement of Stockholders' Equity (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" id="Role_NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock">
        <link:definition>110 - Disclosure - Nature of Operations and Basis of Presentation</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" id="Role_NotesToFinancialStatementsNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock">
        <link:definition>111 - Disclosure - Effect of New Accounting Pronouncements</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsBusinessCombinationDisclosureTextBlock" id="Role_NotesToFinancialStatementsBusinessCombinationDisclosureTextBlock">
        <link:definition>112 - Disclosure - Business Combinations</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsOtherCurrentAssetsTextBlock" id="Role_NotesToFinancialStatementsOtherCurrentAssetsTextBlock">
        <link:definition>113 - Disclosure - Other Current Assets</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlock" id="Role_NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlock">
        <link:definition>114 - Disclosure - Intangible Assets</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsDebtDisclosureTextBlock" id="Role_NotesToFinancialStatementsDebtDisclosureTextBlock">
        <link:definition>115 - Disclosure - Credit and Other Debt Agreements</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlock" id="Role_NotesToFinancialStatementsEarningsPerShareTextBlock">
        <link:definition>116 - Disclosure - Earnings Per Share</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsStockOptionPlansTextBlock" id="Role_NotesToFinancialStatementsStockOptionPlansTextBlock">
        <link:definition>117 - Disclosure - Stock Option Plans</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsCompensationRelatedCostsGeneralTextBlock" id="Role_NotesToFinancialStatementsCompensationRelatedCostsGeneralTextBlock">
        <link:definition>118 - Disclosure - Deferred Compensation</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsRestrictedStockAndCashAwardsTextBlock" id="Role_NotesToFinancialStatementsRestrictedStockAndCashAwardsTextBlock">
        <link:definition>119 - Disclosure - Restricted Stock, Performance Share and Cash Awards</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsEquityMethodInvestmentsDisclosureTextBlock" id="Role_NotesToFinancialStatementsEquityMethodInvestmentsDisclosureTextBlock">
        <link:definition>120 - Disclosure - Investments</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsDerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" id="Role_NotesToFinancialStatementsDerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock">
        <link:definition>121 - Disclosure - Derivatives and Hedging Activity</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlock" id="Role_NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlock">
        <link:definition>122 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock" id="Role_NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock">
        <link:definition>123 - Disclosure - Accumulated Other Comprehensive Earnings (Loss)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlock" id="Role_NotesToFinancialStatementsSegmentReportingDisclosureTextBlock">
        <link:definition>124 - Disclosure - Segment Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlockPolicies" id="Role_NotesToFinancialStatementsNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlockPolicies">
        <link:definition>125 - Disclosure - Effect of New Accounting Pronouncements (Policies)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsBusinessCombinationDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsBusinessCombinationDisclosureTextBlockTables">
        <link:definition>126 - Disclosure - Business Combinations (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsOtherCurrentAssetsTextBlockTables" id="Role_NotesToFinancialStatementsOtherCurrentAssetsTextBlockTables">
        <link:definition>127 - Disclosure - Other Current Assets (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlockTables">
        <link:definition>128 - Disclosure - Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsDebtDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsDebtDisclosureTextBlockTables">
        <link:definition>129 - Disclosure - Credit and Other Debt Agreements (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlockTables" id="Role_NotesToFinancialStatementsEarningsPerShareTextBlockTables">
        <link:definition>130 - Disclosure - Earnings Per Share (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsStockOptionPlansTextBlockTables" id="Role_NotesToFinancialStatementsStockOptionPlansTextBlockTables">
        <link:definition>131 - Disclosure - Stock Option Plans (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsEquityMethodInvestmentsDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsEquityMethodInvestmentsDisclosureTextBlockTables">
        <link:definition>132 - Disclosure - Investments (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsDerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsDerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlockTables">
        <link:definition>133 - Disclosure - Derivatives and Hedging Activity (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlockTables">
        <link:definition>134 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlockTables" id="Role_NotesToFinancialStatementsComprehensiveIncomeNoteTextBlockTables">
        <link:definition>135 - Disclosure - Accumulated Other Comprehensive Earnings (Loss) (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlockTables" id="Role_NotesToFinancialStatementsSegmentReportingDisclosureTextBlockTables">
        <link:definition>136 - Disclosure - Segment Information (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureNatureOfOperationsAndBasisOfPresentationAdditionalInformation" id="DisclosureNatureOfOperationsAndBasisOfPresentationAdditionalInformation">
        <link:definition>137 - Disclosure - Nature of Operations and Basis of Presentation - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureEffectOfNewAccountingPronouncementsAdditionalInformation" id="DisclosureEffectOfNewAccountingPronouncementsAdditionalInformation">
        <link:definition>138 - Disclosure - Effect of New Accounting Pronouncements - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureBusinessCombinationsAcquisitionMethodForRecordingBusinessCombinations" id="DisclosureBusinessCombinationsAcquisitionMethodForRecordingBusinessCombinations">
        <link:definition>139 - Disclosure - Business Combinations - Acquisition Method for Recording Business Combinations (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureBusinessCombinationsAcquisitionMethodForRecordingBusinessCombinationsParenthetical" id="DisclosureBusinessCombinationsAcquisitionMethodForRecordingBusinessCombinationsParenthetical">
        <link:definition>140 - Disclosure - Business Combinations - Acquisition Method for Recording Business Combinations (Parenthetical) (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureBusinessCombinationsAdditionalInformation" id="DisclosureBusinessCombinationsAdditionalInformation">
        <link:definition>141 - Disclosure - Business Combinations - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureBusinessCombinationsSummaryOfEstimatedFairValuesOfNetAssetsAcquired" id="DisclosureBusinessCombinationsSummaryOfEstimatedFairValuesOfNetAssetsAcquired">
        <link:definition>142 - Disclosure - Business Combinations - Summary of Estimated Fair Values of Net Assets Acquired (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureBusinessCombinationsSummaryOfUnauditedProFormaHistoricalResults" id="DisclosureBusinessCombinationsSummaryOfUnauditedProFormaHistoricalResults">
        <link:definition>143 - Disclosure - Business Combinations - Summary of Unaudited Pro Forma Historical Results (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureOtherCurrentAssetsSummaryOfMajorClassesOfOtherCurrentAssets" id="DisclosureOtherCurrentAssetsSummaryOfMajorClassesOfOtherCurrentAssets">
        <link:definition>144 - Disclosure - Other Current Assets - Summary of Major Classes of Other Current Assets (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureOtherCurrentAssetsAdditionalInformation" id="DisclosureOtherCurrentAssetsAdditionalInformation">
        <link:definition>145 - Disclosure - Other Current Assets - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureIntangibleAssetsCarryingAmountOfGoodwillAllocatedByDomesticAndForeignOperations" id="DisclosureIntangibleAssetsCarryingAmountOfGoodwillAllocatedByDomesticAndForeignOperations">
        <link:definition>146 - Disclosure - Intangible Assets - Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureIntangibleAssetsChangesInCarryingAmountOfGoodwill" id="DisclosureIntangibleAssetsChangesInCarryingAmountOfGoodwill">
        <link:definition>147 - Disclosure - Intangible Assets - Changes in Carrying Amount of Goodwill (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureIntangibleAssetsMajorClassesOfAmortizableIntangibleAssets" id="DisclosureIntangibleAssetsMajorClassesOfAmortizableIntangibleAssets">
        <link:definition>148 - Disclosure - Intangible Assets - Major Classes of Amortizable Intangible Assets (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureIntangibleAssetsEstimatedAggregateAmortizationExpense" id="DisclosureIntangibleAssetsEstimatedAggregateAmortizationExpense">
        <link:definition>149 - Disclosure - Intangible Assets - Estimated Aggregate Amortization Expense (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCreditAndOtherDebtAgreementsSummaryOfCorporateAndOtherDebt" id="DisclosureCreditAndOtherDebtAgreementsSummaryOfCorporateAndOtherDebt">
        <link:definition>150 - Disclosure - Credit and Other Debt Agreements - Summary of Corporate and Other Debt (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCreditAndOtherDebtAgreementsSummaryOfCorporateAndOtherDebtParenthetical" id="DisclosureCreditAndOtherDebtAgreementsSummaryOfCorporateAndOtherDebtParenthetical">
        <link:definition>151 - Disclosure - Credit and Other Debt Agreements - Summary of Corporate and Other Debt (Parenthetical) (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureEarningsPerShareComputationOfBasicAndDilutedNetEPS" id="DisclosureEarningsPerShareComputationOfBasicAndDilutedNetEPS">
        <link:definition>152 - Disclosure - Earnings Per Share - Computation of Basic and Diluted Net EPS (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureEarningsPerShareAdditionalInformation" id="DisclosureEarningsPerShareAdditionalInformation">
        <link:definition>153 - Disclosure - Earnings Per Share - Additional information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureStockOptionPlansAdditionalInformation" id="DisclosureStockOptionPlansAdditionalInformation">
        <link:definition>154 - Disclosure - Stock Option Plans - Additional information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureStockOptionPlansBlackScholesOptionPricingModelWithWeightedAverage" id="DisclosureStockOptionPlansBlackScholesOptionPricingModelWithWeightedAverage">
        <link:definition>155 - Disclosure - Stock Option Plans - Black-Scholes Option Pricing Model with Weighted Average (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureStockOptionPlansStockOptionActivityAndRelatedInformation" id="DisclosureStockOptionPlansStockOptionActivityAndRelatedInformation">
        <link:definition>156 - Disclosure - Stock Option Plans - Stock Option Activity and Related Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureStockOptionPlansStockOptionsOutstandingAndExercisable" id="DisclosureStockOptionPlansStockOptionsOutstandingAndExercisable">
        <link:definition>157 - Disclosure - Stock Option Plans - Stock Options Outstanding and Exercisable (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureDeferredCompensationAdditionalInformation" id="DisclosureDeferredCompensationAdditionalInformation">
        <link:definition>158 - Disclosure - Deferred Compensation - Additional information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureRestrictedStockPerformanceShareAndCashAwardsAdditionalInformation" id="DisclosureRestrictedStockPerformanceShareAndCashAwardsAdditionalInformation">
        <link:definition>159 - Disclosure - Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureInvestmentsInvestmentsReportedInOtherCurrentAndNonCurrentAssets" id="DisclosureInvestmentsInvestmentsReportedInOtherCurrentAndNonCurrentAssets">
        <link:definition>160 - Disclosure - Investments - Investments Reported in Other Current and Non-Current Assets (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureInvestmentsInvestmentsReportedInOtherCurrentAndNonCurrentAssetsParenthetical" id="DisclosureInvestmentsInvestmentsReportedInOtherCurrentAndNonCurrentAssetsParenthetical">
        <link:definition>161 - Disclosure - Investments - Investments Reported in Other Current and Non-Current Assets (Parenthetical) (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureDerivativesAndHedgingActivitySummaryOfNotionalAndFairValuesOfDerivativeInstruments" id="DisclosureDerivativesAndHedgingActivitySummaryOfNotionalAndFairValuesOfDerivativeInstruments">
        <link:definition>162 - Disclosure - Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureDerivativesAndHedgingActivitySummaryOfNotionalAndFairValuesOfDerivativeInstrumentsParenthetical" id="DisclosureDerivativesAndHedgingActivitySummaryOfNotionalAndFairValuesOfDerivativeInstrumentsParenthetical">
        <link:definition>163 - Disclosure - Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Parenthetical) (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureDerivativesAndHedgingActivitySummaryOfAmountsOfDerivativeGainsLossesRecognizedInAccumulatedOtherComprehensiveLoss" id="DisclosureDerivativesAndHedgingActivitySummaryOfAmountsOfDerivativeGainsLossesRecognizedInAccumulatedOtherComprehensiveLoss">
        <link:definition>164 - Disclosure - Derivatives and Hedging Activity - Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureDerivativesAndHedgingActivityAdditionalInformation" id="DisclosureDerivativesAndHedgingActivityAdditionalInformation">
        <link:definition>165 - Disclosure - Derivatives and Hedging Activity - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsContractualObligations" id="DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsContractualObligations">
        <link:definition>166 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements - Contractual Obligations (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsAdditionalInformation" id="DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsAdditionalInformation">
        <link:definition>167 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsOffBalanceSheetCommitments" id="DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsOffBalanceSheetCommitments">
        <link:definition>168 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements - Off-Balance Sheet Commitments (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsLitigationRegulatoryAndTaxationMattersAdditionalInformation" id="DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsLitigationRegulatoryAndTaxationMattersAdditionalInformation">
        <link:definition>169 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements - Litigation, Regulatory and Taxation Matters- Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsContingentLiabilitiesAdditionalInformation" id="DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsContingentLiabilitiesAdditionalInformation">
        <link:definition>170 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements - Contingent Liabilities - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsTaxAdvantagedInvestmentsNoLongerHeldAdditionalInformation" id="DisclosureCommitmentsContingenciesAndOffBalanceSheetArrangementsTaxAdvantagedInvestmentsNoLongerHeldAdditionalInformation">
        <link:definition>171 - Disclosure - Commitments, Contingencies and Off-Balance Sheet Arrangements - Tax - advantaged Investments No Longer Held - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureAccumulatedOtherComprehensiveEarningsScheduleOfAccumulatedOtherComprehensiveEarningsLossAttributableToControllingInterests" id="DisclosureAccumulatedOtherComprehensiveEarningsScheduleOfAccumulatedOtherComprehensiveEarningsLossAttributableToControllingInterests">
        <link:definition>172 - Disclosure - Accumulated Other Comprehensive Earnings - Schedule of Accumulated Other Comprehensive Earnings (Loss) Attributable to Controlling Interests (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureAccumulatedOtherComprehensiveEarningsAdditionalInformation" id="DisclosureAccumulatedOtherComprehensiveEarningsAdditionalInformation">
        <link:definition>173 - Disclosure - Accumulated Other Comprehensive Earnings - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureSegmentInformationAdditionalInformation" id="DisclosureSegmentInformationAdditionalInformation">
        <link:definition>174 - Disclosure - Segment Information - Additional Information (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.ajg.com/taxonomy/role/DisclosureSegmentInformationScheduleOfSegmentReportingInformationBySegment" id="DisclosureSegmentInformationScheduleOfSegmentReportingInformationBySegment">
        <link:definition>175 - Disclosure - Segment Information - Schedule of Segment Reporting Information by Segment (Detail)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:href="ajg-20170331_cal.xml" xlink:title="Calculation Links, all"/>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:href="ajg-20170331_def.xml" xlink:title="Definition Links, all"/>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:href="ajg-20170331_lab.xml" xlink:title="Label Links, all"/>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:href="ajg-20170331_pre.xml" xlink:title="Presentation Links, all"/>
    </appinfo>
  </annotation>
  <import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <import namespace="http://fasb.org/us-types/2016-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2016/elts/us-types-2016-01-31.xsd"/>
  <import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd"/>
  <import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd"/>
  <import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <import namespace="http://fasb.org/us-gaap/2016-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/country/2016-01-31" schemaLocation="http://xbrl.sec.gov/country/2016/country-2016-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/currency/2016-01-31" schemaLocation="http://xbrl.sec.gov/currency/2016/currency-2016-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/dei/2014-01-31" schemaLocation="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/exch/2016-01-31" schemaLocation="http://xbrl.sec.gov/exch/2016/exch-2016-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/invest/2013-01-31" schemaLocation="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/naics/2011-01-31" schemaLocation="http://xbrl.sec.gov/naics/2011/naics-2011-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/sic/2011-01-31" schemaLocation="http://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/stpr/2011-01-31" schemaLocation="http://xbrl.sec.gov/stpr/2011/stpr-2011-01-31.xsd"/>
  <element name="AccountingStandardsUpdate201609Member" id="ajg_AccountingStandardsUpdate201609Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AccruedCompensationAndOtherAccruedLiabilities" id="ajg_AccruedCompensationAndOtherAccruedLiabilities" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AccruedSupplementalDirectBillAndOtherReceivablesCurrent" id="ajg_AccruedSupplementalDirectBillAndOtherReceivablesCurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AcquiredPropertyThroughLeaseArea" id="ajg_AcquiredPropertyThroughLeaseArea" type="num:areaItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AcquiredPropertyThroughLeasePercentage" id="ajg_AcquiredPropertyThroughLeasePercentage" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AgeOfEmployeeNoLongerSubjectToAwardForfeitureOnConditionCompliance" id="ajg_AgeOfEmployeeNoLongerSubjectToAwardForfeitureOnConditionCompliance" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmortizationOfDeferredCompensationAndRestrictedStock" id="ajg_AmortizationOfDeferredCompensationAndRestrictedStock" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitments" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitments" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFive" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFive" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFour" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFour" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearOne" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearOne" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThereafter" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThereafter" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThree" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThree" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearTwo" id="ajg_AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearTwo" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AnnualActivityOfStockOptionPlansTable" id="ajg_AnnualActivityOfStockOptionPlansTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="AudDenominatedTrancheMember" id="ajg_AudDenominatedTrancheMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BlackScholesOptionPricingModelMember" id="ajg_BlackScholesOptionPricingModelMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BrokerageSegmentMember" id="ajg_BrokerageSegmentMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionActualRevenueAndPreTaxIncomeLossLineItems" id="ajg_BusinessAcquisitionActualRevenueAndPreTaxIncomeLossLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionActualRevenueAndPreTaxIncomeLossTable" id="ajg_BusinessAcquisitionActualRevenueAndPreTaxIncomeLossTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="BusinessAcquisitionCostOfAcquiredEntityPurchasePriceNet" id="ajg_BusinessAcquisitionCostOfAcquiredEntityPurchasePriceNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionEffectiveDateOfAcquisitionYear" id="ajg_BusinessAcquisitionEffectiveDateOfAcquisitionYear" type="xbrli:gYearItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionMember" id="ajg_BusinessAcquisitionMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionPurchasePriceAllocationGoodwillNotExpectedTaxDeductibleAmount" id="ajg_BusinessAcquisitionPurchasePriceAllocationGoodwillNotExpectedTaxDeductibleAmount" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionsProFormaNetIncomeLossToControllingInterest" id="ajg_BusinessAcquisitionsProFormaNetIncomeLossToControllingInterest" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionsPurchasePriceAllocationGoodwillAmount" id="ajg_BusinessAcquisitionsPurchasePriceAllocationGoodwillAmount" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessCombinationAggregateEarnoutObligationMaximum" id="ajg_BusinessCombinationAggregateEarnoutObligationMaximum" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessCombinationAggregateEarnoutObligationRecordedMaximum" id="ajg_BusinessCombinationAggregateEarnoutObligationRecordedMaximum" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessCombinationAnnualizeRevenue" id="ajg_BusinessCombinationAnnualizeRevenue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CarryingAmountOfGoodwillAllocatedByDomesticAndForeignOperationsTableTextBlock" id="ajg_CarryingAmountOfGoodwillAllocatedByDomesticAndForeignOperationsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CashAndEquityAwardWithAggregateFairValueVestedAndDistributedToParticipants" id="ajg_CashAndEquityAwardWithAggregateFairValueVestedAndDistributedToParticipants" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CashAwardsMember" id="ajg_CashAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CashAwardsPerformancePeriod" id="ajg_CashAwardsPerformancePeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CashBasedCompensationAwardExpenses" id="ajg_CashBasedCompensationAwardExpenses" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CashSettledPerformanceSharesMember" id="ajg_CashSettledPerformanceSharesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ChangeInEstimatedAcquisitionEarnoutPayables" id="ajg_ChangeInEstimatedAcquisitionEarnoutPayables" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ChemModInternationalLlcMember" id="ajg_ChemModInternationalLlcMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ChemModLlcMember" id="ajg_ChemModLlcMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CleanCoalInvestmentsMember" id="ajg_CleanCoalInvestmentsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CollateralizedDelinquencyReceivablesPeriod" id="ajg_CollateralizedDelinquencyReceivablesPeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CommissionRevenueMember" id="ajg_CommissionRevenueMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="Commissions" id="ajg_Commissions" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CommitmentsContingenciesAndOffBalanceSheetArrangementsLineItems" id="ajg_CommitmentsContingenciesAndOffBalanceSheetArrangementsLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CommitmentsContingenciesAndOffBalanceSheetArrangementsTable" id="ajg_CommitmentsContingenciesAndOffBalanceSheetArrangementsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationLineItems" id="ajg_CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationTable" id="ajg_CommonStockOptionsRestrictedStockWarrantsAndChangesInCapitalizationTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="CompensationApprovedByCommitteeValue" id="ajg_CompensationApprovedByCommitteeValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CompensationExpenseMember" id="ajg_CompensationExpenseMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ConstructionRiskSolutionsLLCMember" id="ajg_ConstructionRiskSolutionsLLCMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ContingentCommissions" id="ajg_ContingentCommissions" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ContractualObligationsMember" id="ajg_ContractualObligationsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ControllingInterestMember" id="ajg_ControllingInterestMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CreditAgreementMember" id="ajg_CreditAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DebtObligationMember" id="ajg_DebtObligationMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredCashParticipationPlanMember" id="ajg_DeferredCashParticipationPlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredCompensationAndRestrictedStockExpensesBenefit" id="ajg_DeferredCompensationAndRestrictedStockExpensesBenefit" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredCompensationAndRestrictedStockInShares" id="ajg_DeferredCompensationAndRestrictedStockInShares" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredEquityParticipationPlanDistributionsToKeyExecutivesAge" id="ajg_DeferredEquityParticipationPlanDistributionsToKeyExecutivesAge" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredEquityParticipationPlanMember" id="ajg_DeferredEquityParticipationPlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredEquityParticipationPlanSubPlansMember" id="ajg_DeferredEquityParticipationPlanSubPlansMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredEquityParticipationSubPlanDistributionsRequisiteServiceDescription" id="ajg_DeferredEquityParticipationSubPlanDistributionsRequisiteServiceDescription" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredEquityParticipationSubPlanDistributionsToKeyExecutivesAge" id="ajg_DeferredEquityParticipationSubPlanDistributionsToKeyExecutivesAge" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DocumentAndEntityInformationAbstract" id="ajg_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EarnoutPaymentsForAcquisitions" id="ajg_EarnoutPaymentsForAcquisitions" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EquityMethodInvestmentSummarizedFinancialInformationFundingCommitments" id="ajg_EquityMethodInvestmentSummarizedFinancialInformationFundingCommitments" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ErrorsAndOmissionsMember" id="ajg_ErrorsAndOmissionsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EstimatedAggregateAmortizationExpenseTableTextBlock" id="ajg_EstimatedAggregateAmortizationExpenseTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ExercisePriceOfStockOptionsPercentOfFairMarketValueOfShareOfCommonStockOnDateOfGrant" id="ajg_ExercisePriceOfStockOptionsPercentOfFairMarketValueOfShareOfCommonStockOnDateOfGrant" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ExpirationLists" id="ajg_ExpirationLists" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ExpirationListsMember" id="ajg_ExpirationListsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FacilityAndFacilityMember" id="ajg_FacilityAndFacilityMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FacilityBMember" id="ajg_FacilityBMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueInputsAttritionRate" id="ajg_FairValueInputsAttritionRate" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FirstInstallmentMember" id="ajg_FirstInstallmentMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFivePointEightFivePercentFiftyMillionDollarsDueNovemberThirtyTwoThousandEighteenAndNovemberThirtyTwoThousandNineteenMember" id="ajg_FixedRateOfFivePointEightFivePercentFiftyMillionDollarsDueNovemberThirtyTwoThousandEighteenAndNovemberThirtyTwoThousandNineteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFivePointFourNinePercentBalloonDueFebruaryTenTwoThousandTwentyThreeMember" id="ajg_FixedRateOfFivePointFourNinePercentBalloonDueFebruaryTenTwoThousandTwentyThreeMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFivePointOneEightPercentBalloonDueFebruaryTenTwoThousandTwentyOneMember" id="ajg_FixedRateOfFivePointOneEightPercentBalloonDueFebruaryTenTwoThousandTwentyOneMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointFiveEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyFourMember" id="ajg_FixedRateOfFourPointFiveEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyFourMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointFiveFivePercentBalloonDueJuneTwoTwoThousandTwentyEightMember" id="ajg_FixedRateOfFourPointFiveFivePercentBalloonDueJuneTwoTwoThousandTwentyEightMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointFourZeroPercentBalloonDueJuneTwoTwoThousandTwentySixMember" id="ajg_FixedRateOfFourPointFourZeroPercentBalloonDueJuneTwoTwoThousandTwentySixMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointNineEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyNineMember" id="ajg_FixedRateOfFourPointNineEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyNineMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointOneThreePercentageBalloonDueJuneTwentyFourTwoThousandTwentyThreeMember" id="ajg_FixedRateOfFourPointOneThreePercentageBalloonDueJuneTwentyFourTwoThousandTwentyThreeMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointSevenThreePercentBalloonDueFebruaryTwentySevenTwoThousandTwentySixMember" id="ajg_FixedRateOfFourPointSevenThreePercentBalloonDueFebruaryTwentySevenTwoThousandTwentySixMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointSevenZeroPercentBalloonDueJuneTwoTwoThousandThirtyOneMember" id="ajg_FixedRateOfFourPointSevenZeroPercentBalloonDueJuneTwoTwoThousandThirtyOneMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointThreeOnePercentBalloonDueJuneTwentyFourTwoThousandTwentyFiveMember" id="ajg_FixedRateOfFourPointThreeOnePercentBalloonDueJuneTwentyFourTwoThousandTwentyFiveMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfFourPointThreeSixPercentBalloonDueJuneTwentyFourTwoThousandTwentySixMember" id="ajg_FixedRateOfFourPointThreeSixPercentBalloonDueJuneTwentyFourTwoThousandTwentySixMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfSixPointFourFourPercentBalloonDueAugustThreeTwoThousandSeventeenMember" id="ajg_FixedRateOfSixPointFourFourPercentBalloonDueAugustThreeTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfThreePointFourEightPercentBalloonDueJuneTwentyFourTwoThousandTwentyMember" id="ajg_FixedRateOfThreePointFourEightPercentBalloonDueJuneTwentyFourTwoThousandTwentyMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfThreePointFourSixPercentageBalloonDueDecemberOneTwoThousandTwentySevenMember" id="ajg_FixedRateOfThreePointFourSixPercentageBalloonDueDecemberOneTwoThousandTwentySevenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfThreePointNineNinePercentBalloonDueJulyTenTwoThousandTwentyMember" id="ajg_FixedRateOfThreePointNineNinePercentBalloonDueJulyTenTwoThousandTwentyMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfThreePointSixNinePercentBalloonDueJuneFourteenTwoThousandTwentyTwoMember" id="ajg_FixedRateOfThreePointSixNinePercentBalloonDueJuneFourteenTwoThousandTwentyTwoMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfThreePointTwoZeroPercentBalloonDueJuneTwentyFourTwoThousandNineteenMember" id="ajg_FixedRateOfThreePointTwoZeroPercentBalloonDueJuneTwentyFourTwoThousandNineteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FixedRateOfTwoPointEightZeroPercentBalloonDueJuneTwentyFourTwoThousandEighteenMember" id="ajg_FixedRateOfTwoPointEightZeroPercentBalloonDueJuneTwentyFourTwoThousandEighteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FourteenTwoThousandNineEraCleanCoalProductionPlantsMember" id="ajg_FourteenTwoThousandNineEraCleanCoalProductionPlantsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FundingCommitmentsMember" id="ajg_FundingCommitmentsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FutureAmortizationExpenseOfFiscalYear" id="ajg_FutureAmortizationExpenseOfFiscalYear" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="GoodwillRelatedToNondeductibleAmortizableIntangibleAssets" id="ajg_GoodwillRelatedToNondeductibleAmortizableIntangibleAssets" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="HillChessonAndWoodyMember" id="ajg_HillChessonAndWoodyMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InsuranceBrokerageAndRiskManagementServicesMember" id="ajg_InsuranceBrokerageAndRiskManagementServicesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InterbankRatesPlusOnePointZeroFivePercentExpiresMayEighteenTwoThousandSeventeenMember" id="ajg_InterbankRatesPlusOnePointZeroFivePercentExpiresMayEighteenTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InterbankRatesPlusZeroPointFiveFivePercentExpiresMayEighteenTwoThousandSeventeenMember" id="ajg_InterbankRatesPlusZeroPointFiveFivePercentExpiresMayEighteenTwoThousandSeventeenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InterestOnDebtMember" id="ajg_InterestOnDebtMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InvestmentsAndEmployeeDeferredCompensationPlanLineItems" id="ajg_InvestmentsAndEmployeeDeferredCompensationPlanLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InvestmentsAndEmployeeDeferredCompensationPlanTable" id="ajg_InvestmentsAndEmployeeDeferredCompensationPlanTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="LessSubleaseArrangementsMember" id="ajg_LessSubleaseArrangementsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LettersOfCreditMember" id="ajg_LettersOfCreditMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LiabilitiesRecordedOnSelfInsurance" id="ajg_LiabilitiesRecordedOnSelfInsurance" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearSeven" id="ajg_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearSeven" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearSix" id="ajg_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearSix" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LongTermIncentivePlanMember" id="ajg_LongTermIncentivePlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumPotentialEarnoutPayable" id="ajg_MaximumPotentialEarnoutPayable" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MicroCaptiveInsuranceCompaniesManaged" id="ajg_MicroCaptiveInsuranceCompaniesManaged" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NetChangeInAccruedCompensationAndOtherAccruedLiabilities" id="ajg_NetChangeInAccruedCompensationAndOtherAccruedLiabilities" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NetChangeInFeesReceivableUnearnedFees" id="ajg_NetChangeInFeesReceivableUnearnedFees" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NetProceedsFromSalesOfOperations" id="ajg_NetProceedsFromSalesOfOperations" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NineOtherAcquisitionsMember" id="ajg_NineOtherAcquisitionsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NineteenTwoThousandElevenEraCleanCoalProductionPlantsMember" id="ajg_NineteenTwoThousandElevenEraCleanCoalProductionPlantsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NotePurchaseAgreementMember" id="ajg_NotePurchaseAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfCoalPlants" id="ajg_NumberOfCoalPlants" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfCountriesInWhichCompanyDoesBusinessThroughNetworkOfCorrespondentBrokersAndConsultants" id="ajg_NumberOfCountriesInWhichCompanyDoesBusinessThroughNetworkOfCorrespondentBrokersAndConsultants" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfCountriesInWhichCompanyHasOperations" id="ajg_NumberOfCountriesInWhichCompanyHasOperations" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfEmployees" id="ajg_NumberOfEmployees" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfLetterOfCreditIssued" id="ajg_NumberOfLetterOfCreditIssued" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfSquareFeet" id="ajg_NumberOfSquareFeet" type="num:areaItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfVariableInterestEntities" id="ajg_NumberOfVariableInterestEntities" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NzdDenominatedTrancheMember" id="ajg_NzdDenominatedTrancheMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OneTwoThousandElevenEraCleanCoalProductionPlantsMember" id="ajg_OneTwoThousandElevenEraCleanCoalProductionPlantsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OperatingLeaseCommitmentExpirationDate" id="ajg_OperatingLeaseCommitmentExpirationDate" type="xbrli:dateItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OperatingLeaseObligationMember" id="ajg_OperatingLeaseObligationMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OptionsOrStockAppreciationRightsMember" id="ajg_OptionsOrStockAppreciationRightsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OptionsToPurchaseCommonStockSharesOutstanding" id="ajg_OptionsToPurchaseCommonStockSharesOutstanding" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OtherForeignMember" id="ajg_OtherForeignMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OutstandingPurchaseObligationsMember" id="ajg_OutstandingPurchaseObligationsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OutstandingPurchaseObligationsRelatedToNewCorporateHeadquartersMember" id="ajg_OutstandingPurchaseObligationsRelatedToNewCorporateHeadquartersMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PerformanceBasedRestrictedStockMember" id="ajg_PerformanceBasedRestrictedStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PeriodForOptionsToExpireFromDateOfGrant" id="ajg_PeriodForOptionsToExpireFromDateOfGrant" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PeriodOfServiceFromGrantDateStockOptionsAwardedNotSubjectToForfeiture" id="ajg_PeriodOfServiceFromGrantDateStockOptionsAwardedNotSubjectToForfeiture" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PremiumFinancingBorrowings" id="ajg_PremiumFinancingBorrowings" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PremiumFinancingDebtFacilityMember" id="ajg_PremiumFinancingDebtFacilityMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PremiumsPayableToInsuranceAndReinsuranceCompanies" id="ajg_PremiumsPayableToInsuranceAndReinsuranceCompanies" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PresidioGroupIncMember" id="ajg_PresidioGroupIncMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PrimeOrLiborPlusUpToOnePointFourFivePercentExpiresAprilEightTwoThousandSixteenMember" id="ajg_PrimeOrLiborPlusUpToOnePointFourFivePercentExpiresAprilEightTwoThousandSixteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PropertyTaxCreditExpectToReceive" id="ajg_PropertyTaxCreditExpectToReceive" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PropertyTaxCreditExpectToReceivePeriod" id="ajg_PropertyTaxCreditExpectToReceivePeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeUnits" id="ajg_ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeUnits" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeValue" id="ajg_ProvisionalCompensationCashAwardApprovedForFutureGrantByCompensationCommitteeValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="Range01Member" id="ajg_Range01Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="Range02Member" id="ajg_Range02Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="Range03Member" id="ajg_Range03Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="Range04Member" id="ajg_Range04Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RecordedEarnOutPayable" id="ajg_RecordedEarnOutPayable" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RefinedCoalProductionRelatedReceivablesCurrent" id="ajg_RefinedCoalProductionRelatedReceivablesCurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RentCaptiveFacilityMember" id="ajg_RentCaptiveFacilityMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestrictedStockAndCashAwardsTextBlock" id="ajg_RestrictedStockAndCashAwardsTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestrictedStockPlanMember" id="ajg_RestrictedStockPlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestrictedStockUnitsRsusMember" id="ajg_RestrictedStockUnitsRsusMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RevenuesFromCleanCoalActivities" id="ajg_RevenuesFromCleanCoalActivities" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RiskManagementSegmentMember" id="ajg_RiskManagementSegmentMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfBlackScholesOptionPricingModelWithWeightedAverageTableTextBlock" id="ajg_ScheduleOfBlackScholesOptionPricingModelWithWeightedAverageTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfBusinessAcquisitionAcquisitionOfAssetsTableTextBlock" id="ajg_ScheduleOfBusinessAcquisitionAcquisitionOfAssetsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfBusinessAcquisitionProFormaTableTextBlock" id="ajg_ScheduleOfBusinessAcquisitionProFormaTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfDebtDisclosureTableTextBlock" id="ajg_ScheduleOfDebtDisclosureTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfOffBalanceSheetCommitmentsTableTextBlock" id="ajg_ScheduleOfOffBalanceSheetCommitmentsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfSaleOfSubsidiaryAbstract" id="ajg_ScheduleOfSaleOfSubsidiaryAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfStockOptionActivityAndRelatedInformationTableTextBlock" id="ajg_ScheduleOfStockOptionActivityAndRelatedInformationTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfStockOptionsOutstandingAndExercisableTableTextBlock" id="ajg_ScheduleOfStockOptionsOutstandingAndExercisableTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SecondInstallmentMember" id="ajg_SecondInstallmentMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SecurityDepositMember" id="ajg_SecurityDepositMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SelfInsuranceDeductiblesMember" id="ajg_SelfInsuranceDeductiblesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SemiAnnualPaymentsOfInterest" id="ajg_SemiAnnualPaymentsOfInterest" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SemiAnnualPaymentsOfInterestNet" id="ajg_SemiAnnualPaymentsOfInterestNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateFairValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateFairValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingDate" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingDate" type="xbrli:dateItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionNonvestedIntrinsicValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionNonvestedIntrinsicValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAmountPayablePerEmployee" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAmountPayablePerEmployee" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearOne" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearOne" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearThree" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearThree" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearTwo" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePercentageYearTwo" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingFairValue" id="ajg_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingFairValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="StatementsOfCashFlowsPolicyPolicyTextBlock" id="ajg_StatementsOfCashFlowsPolicyPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="StockOptionPlansLineItems" id="ajg_StockOptionPlansLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="StockOptionPlansTextBlock" id="ajg_StockOptionPlansTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="StockSettledPerformanceSharesMember" id="ajg_StockSettledPerformanceSharesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SummaryOfNotionalAndFairValuesOfDerivativeInstrumentsTableTextBlock" id="ajg_SummaryOfNotionalAndFairValuesOfDerivativeInstrumentsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SupplementalCommissions" id="ajg_SupplementalCommissions" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TaxImpactFromIssuanceOfCommonStock" id="ajg_TaxImpactFromIssuanceOfCommonStock" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TaxIncrementFinancingMember" id="ajg_TaxIncrementFinancingMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFifteenProvisionalCashAwardsMember" id="ajg_TwoThousandFifteenProvisionalCashAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFourteenProvisionalCashAwardsMember" id="ajg_TwoThousandFourteenProvisionalCashAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandSeventeenAcquisitionsMember" id="ajg_TwoThousandSeventeenAcquisitionsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandSeventeenProvisionalCashAwardsMember" id="ajg_TwoThousandSeventeenProvisionalCashAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandSixteenAcquisitionsMember" id="ajg_TwoThousandSixteenAcquisitionsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandSixteenProvisionalCashAwardsMember" id="ajg_TwoThousandSixteenProvisionalCashAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandThirteenProvisionalCashAwardsMember" id="ajg_TwoThousandThirteenProvisionalCashAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UltimateAwardValueMultiplesOfOriginalValueOfUnitsMaximum" id="ajg_UltimateAwardValueMultiplesOfOriginalValueOfUnitsMaximum" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UltimateAwardValueMultiplesOfOriginalValueOfUnitsMinimum" id="ajg_UltimateAwardValueMultiplesOfOriginalValueOfUnitsMinimum" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnearnedDeferredCompensationShare" id="ajg_UnearnedDeferredCompensationShare" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnearnedDeferredCompensationValue" id="ajg_UnearnedDeferredCompensationValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnearnedFees" id="ajg_UnearnedFees" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnearnedRestrictedStockMember" id="ajg_UnearnedRestrictedStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnsecuredMulticurrencyCreditAgreementMember" id="ajg_UnsecuredMulticurrencyCreditAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="VentureCapitalFundsAndOtherMember" id="ajg_VentureCapitalFundsAndOtherMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding" id="ajg_WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WeightedAveragePeriod" id="ajg_WeightedAveragePeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
</schema>
