    <SEC-DOCUMENT>0000950170-24-021164-index.html : 20240227
    <SEC-HEADER>0000950170-24-021164.hdr.sgml : 20240227
    <ACCEPTANCE-DATETIME>20240227161555
    ACCESSION NUMBER:		0000950170-24-021164
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		16
    CONFORMED PERIOD OF REPORT:	20240227
    ITEM INFORMATION:		Results of Operations and Financial Condition
    ITEM INFORMATION:		Regulation FD Disclosure
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20240227
    DATE AS OF CHANGE:		20240227

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Metallus Inc.
    		CENTRAL INDEX KEY:			0001598428
    		STANDARD INDUSTRIAL CLASSIFICATION:	STEEL WORKS, BLAST FURNACES  ROLLING MILLS (COKE OVENS) [3312]
    		ORGANIZATION NAME:           	04 Manufacturing
    		IRS NUMBER:				464024951
    		STATE OF INCORPORATION:			OH
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-36313
    		FILM NUMBER:		24686948

    	BUSINESS ADDRESS:
    		STREET 1:		1835 DUEBER AVENUE SW
    		CITY:			CANTON
    		STATE:			OH
    		ZIP:			44706-0928
    		BUSINESS PHONE:		330-471-7000

    	MAIL ADDRESS:
    		STREET 1:		1835 DUEBER AVENUE SW
    		CITY:			CANTON
    		STATE:			OH
    		ZIP:			44706-0928

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	TimkenSteel Corp
    		DATE OF NAME CHANGE:	20140128
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>mtus-20240227.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: mtus-20240227.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>2
    <FILENAME>mtus-ex99_1.htm
    <DESCRIPTION>EX-99.1
    <TEXT>
    Document 2 - file: mtus-ex99_1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>img20923151_0.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: img20923151_0.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>4
    <FILENAME>img203915712_0.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 4 - file: img203915712_0.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>5
    <FILENAME>img203915712_1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 5 - file: img203915712_1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>6
    <FILENAME>mtus-20240227.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA WITH EMBEDDED LINKBASES DOCUMENT
    <TEXT>
    Document 6 - file: mtus-20240227.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>7
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 7 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>9
    <FILENAME>Financial_Report.xlsx
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 9 - file: Financial_Report.xlsx

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

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>11
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 11 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>13
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 13 - file: FilingSummary.html

    Document 13 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>15
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 15 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>16
    <FILENAME>0000950170-24-021164-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 16 - file: 0000950170-24-021164-xbrl.zip

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>17
    <FILENAME>mtus-20240227_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 17 - file: mtus-20240227_htm.html

    Document 17 - RAW XML: mtus-20240227_htm.xml

    </DOCUMENT>
    </SEC-DOCUMENT>