    <SEC-DOCUMENT>0001530950-21-000225-index.html : 20210706
    <SEC-HEADER>0001530950-21-000225.hdr.sgml : 20210706
    <ACCEPTANCE-DATETIME>20210706083438
    ACCESSION NUMBER:		0001530950-21-000225
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		16
    CONFORMED PERIOD OF REPORT:	20210701
    ITEM INFORMATION:		Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers
    ITEM INFORMATION:		Regulation FD Disclosure
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20210706
    DATE AS OF CHANGE:		20210706

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Post Holdings, Inc.
    		CENTRAL INDEX KEY:			0001530950
    		STANDARD INDUSTRIAL CLASSIFICATION:	GRAIN MILL PRODUCTS [2040]
    		IRS NUMBER:				453355106
    		STATE OF INCORPORATION:			MO
    		FISCAL YEAR END:			0930

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-35305
    		FILM NUMBER:		211072568

    	BUSINESS ADDRESS:
    		STREET 1:		2503 S. HANLEY ROAD
    		CITY:			ST. LOUIS
    		STATE:			MO
    		ZIP:			63144
    		BUSINESS PHONE:		314-644-7600

    	MAIL ADDRESS:
    		STREET 1:		2503 S. HANLEY ROAD
    		CITY:			ST. LOUIS
    		STATE:			MO
    		ZIP:			63144
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>post-20210701.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: post-20210701.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-10.1
    <SEQUENCE>2
    <FILENAME>ex10-1xstockxsettledrsuagr.htm
    <DESCRIPTION>EX-10.1 - RSU AGREEMENT (CLIFF VESTING)
    <TEXT>
    Document 2 - file: ex10-1xstockxsettledrsuagr.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>3
    <FILENAME>ex991leadershippr.htm
    <DESCRIPTION>EX-99.1 - PRESS RELEASE
    <TEXT>
    Document 3 - file: ex991leadershippr.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>4
    <FILENAME>post-20210701.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
    Document 4 - file: post-20210701.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>5
    <FILENAME>post-20210701_lab.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT
    <TEXT>
    Document 5 - file: post-20210701_lab.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.PRE
    <SEQUENCE>6
    <FILENAME>post-20210701_pre.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT
    <TEXT>
    Document 6 - file: post-20210701_pre.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>image_0.jpg
    <TEXT>
    Document 7 - file: image_0.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>post-20210701_g1.jpg
    <TEXT>
    Document 8 - file: post-20210701_g1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>9
    <FILENAME>post-20210701_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 9 - file: post-20210701_htm.html

    Document 9 - RAW XML: post-20210701_htm.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>10
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 10 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>11
    <FILENAME>Financial_Report.xlsx
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 11 - file: Financial_Report.xlsx

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>12
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 12 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>13
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 13 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>14
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 14 - file: FilingSummary.html

    Document 14 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>16
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 16 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>17
    <FILENAME>0001530950-21-000225-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 17 - file: 0001530950-21-000225-xbrl.zip

    </DOCUMENT>
    </SEC-DOCUMENT>