    <SEC-DOCUMENT>0001530950-25-000284-index.html : 20251215
    <SEC-HEADER>0001530950-25-000284.hdr.sgml : 20251215
    <ACCEPTANCE-DATETIME>20251215070051
    ACCESSION NUMBER:		0001530950-25-000284
    CONFORMED SUBMISSION TYPE:	DEF 14A
    PUBLIC DOCUMENT COUNT:		28
    CONFORMED PERIOD OF REPORT:	20260129
    FILED AS OF DATE:		20251215
    DATE AS OF CHANGE:		20251215

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Post Holdings, Inc.
    		CENTRAL INDEX KEY:			0001530950
    		STANDARD INDUSTRIAL CLASSIFICATION:	GRAIN MILL PRODUCTS [2040]
    		ORGANIZATION NAME:           	04 Manufacturing
    		EIN:				453355106
    		STATE OF INCORPORATION:			MO
    		FISCAL YEAR END:			0930

    	FILING VALUES:
    		FORM TYPE:		DEF 14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-35305
    		FILM NUMBER:		251569970

    	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>DEF 14A
    <SEQUENCE>1
    <FILENAME>post-20251210.htm
    <DESCRIPTION>DEF 14A
    <TEXT>
    Document 1 - file: post-20251210.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>2
    <FILENAME>post-20251210.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
    Document 2 - file: post-20251210.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.DEF
    <SEQUENCE>3
    <FILENAME>post-20251210_def.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION DEFINITION LINKBASE DOCUMENT
    <TEXT>
    Document 3 - file: post-20251210_def.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>4
    <FILENAME>post-20251210_lab.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT
    <TEXT>
    Document 4 - file: post-20251210_lab.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.PRE
    <SEQUENCE>5
    <FILENAME>post-20251210_pre.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT
    <TEXT>
    Document 5 - file: post-20251210_pre.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>post-20251210_g1.gif
    <TEXT>
    Document 6 - file: post-20251210_g1.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>post-20251210_g10.jpg
    <TEXT>
    Document 7 - file: post-20251210_g10.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>post-20251210_g11.jpg
    <TEXT>
    Document 8 - file: post-20251210_g11.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>post-20251210_g12.jpg
    <TEXT>
    Document 9 - file: post-20251210_g12.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>post-20251210_g2.jpg
    <TEXT>
    Document 10 - file: post-20251210_g2.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>post-20251210_g3.jpg
    <TEXT>
    Document 11 - file: post-20251210_g3.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>12
    <FILENAME>post-20251210_g4.gif
    <TEXT>
    Document 12 - file: post-20251210_g4.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>13
    <FILENAME>post-20251210_g5.gif
    <TEXT>
    Document 13 - file: post-20251210_g5.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>14
    <FILENAME>post-20251210_g6.gif
    <TEXT>
    Document 14 - file: post-20251210_g6.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>15
    <FILENAME>post-20251210_g7.jpg
    <TEXT>
    Document 15 - file: post-20251210_g7.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>16
    <FILENAME>post-20251210_g8.jpg
    <TEXT>
    Document 16 - file: post-20251210_g8.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>17
    <FILENAME>post-20251210_g9.jpg
    <TEXT>
    Document 17 - file: post-20251210_g9.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>19
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 19 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>20
    <FILENAME>R2.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 20 - file: R2.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>21
    <FILENAME>R3.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 21 - file: R3.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>22
    <FILENAME>R4.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 22 - file: R4.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>23
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 23 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>24
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 24 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>26
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 26 - file: FilingSummary.html

    Document 26 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>28
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 28 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>29
    <FILENAME>0001530950-25-000284-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 29 - file: 0001530950-25-000284-xbrl.zip

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>30
    <FILENAME>post-20251210_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 30 - file: post-20251210_htm.html

    Document 30 - RAW XML: post-20251210_htm.xml

    </DOCUMENT>
    </SEC-DOCUMENT>