    <SEC-DOCUMENT>0001193125-20-082511-index.html : 20200323
    <SEC-HEADER>0001193125-20-082511.hdr.sgml : 20200323
    <ACCEPTANCE-DATETIME>20200323163121
    ACCESSION NUMBER:		0001193125-20-082511
    CONFORMED SUBMISSION TYPE:	DEF 14A
    PUBLIC DOCUMENT COUNT:		10
    CONFORMED PERIOD OF REPORT:	20200512
    FILED AS OF DATE:		20200323
    DATE AS OF CHANGE:		20200323
    EFFECTIVENESS DATE:		20200323

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Arthur J. Gallagher & Co.
    		CENTRAL INDEX KEY:			0000354190
    		STANDARD INDUSTRIAL CLASSIFICATION:	INSURANCE AGENTS BROKERS & SERVICES [6411]
    		IRS NUMBER:				362151613
    		STATE OF INCORPORATION:			IL
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEF 14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-09761
    		FILM NUMBER:		20735235

    	BUSINESS ADDRESS:
    		STREET 1:		2850 GOLF ROAD
    		CITY:			ROLLING MEADOWS
    		STATE:			IL
    		ZIP:			60008-4050
    		BUSINESS PHONE:		630-773-3800

    	MAIL ADDRESS:
    		STREET 1:		2850 GOLF ROAD
    		CITY:			ROLLING MEADOWS
    		STATE:			IL
    		ZIP:			60008-4050

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	ARTHUR J. GALLAGHER & CO.
    		DATE OF NAME CHANGE:	20190819

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	GALLAGHER ARTHUR J & CO
    		DATE OF NAME CHANGE:	19920703
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEF 14A
    <SEQUENCE>1
    <FILENAME>d857229ddef14a.htm
    <DESCRIPTION>DEF 14A
    <TEXT>
    Document 1 - file: d857229ddef14a.htm

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    <DOCUMENT>
    <TYPE>DEF 14A
    <SEQUENCE>2
    <FILENAME>d857229ddef14a1.pdf
    <DESCRIPTION>COURTESY PDF
    <TEXT>
    Document 2 - file: d857229ddef14a1.pdf

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    <TYPE>GRAPHIC
    <SEQUENCE>3
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    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: g857229dsp0005a.jpg

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    <SEQUENCE>4
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    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 4 - file: g857229g05d48.jpg

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    <SEQUENCE>5
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    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 5 - file: g857229g12r97.jpg

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    <SEQUENCE>6
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    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 6 - file: g857229g33y25.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
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    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: g857229g39c20.jpg

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    <DOCUMENT>
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    <SEQUENCE>8
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    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: g857229g62x84.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>g857229g69o27.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: g857229g69o27.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>g857229g76q21.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: g857229g76q21.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>