<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2026"
  xmlns:fnd="http://xbrl.sec.gov/fnd/2026q3"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="ft13304-20261027.xsd" xlink:type="simple"/>
    <context id="AsOf2026-10-27">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0002148629</identifier>
        </entity>
        <period>
            <startDate>2026-10-27</startDate>
            <endDate>2026-10-27</endDate>
        </period>
    </context>
    <dei:AmendmentFlag contextRef="AsOf2026-10-27" id="Fact000003">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey contextRef="AsOf2026-10-27" id="Fact000004">0002148629</dei:EntityCentralIndexKey>
    <dei:DocumentType contextRef="AsOf2026-10-27" id="Fact000010">S-6</dei:DocumentType>
    <dei:EntityRegistrantName contextRef="AsOf2026-10-27" id="Fact000011">FT 13304</dei:EntityRegistrantName>
    <dei:DocumentPeriodEndDate contextRef="AsOf2026-10-27" id="Fact000012">2026-10-27</dei:DocumentPeriodEndDate>
    <fnd:NmRule35d1TermDfnTextBlock contextRef="AsOf2026-10-27" id="Fact000013">

&lt;p style="font: bold 11pt/12pt Times New Roman, Times, Serif; margin: 4pt 0 1pt"&gt;Objective.&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt; text-indent: 0.25in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;The
Trust seeks above-average capital appreciation by investing in small and mid-cap U.S. companies as defined by Richard Bernstein Advisors
(defined below) in the industrial and community banking sectors. In April 2026, Janus Henderson Group Ltd. (&#x201c;Janus Henderson&#x201d;)
acquired Richard Bernstein Advisors LLC, which became an indirect, wholly-owned subsidiary of Janus Henderson. In connection with the
acquisition, key investment personnel from Richard Bernstein Advisors LLC were transitioned to the Multi-Asset Macro Investing team within
Janus Henderson Investors US LLC (the &#x201c;Portfolio Consultant&#x201d;), an indirect, wholly-owned subsidiary of Janus Henderson (such
team is referred to herein as &#x201c;Richard Bernstein Advisors&#x201d;). Under normal circumstances, the Trust will invest at least 80%
of its assets in U.S. companies. According to Richard Bernstein Advisors, American Industrial Renaissance&lt;sup&gt;&#xae;&lt;/sup&gt; Companies are
U.S. industrial companies focused on infrastructure, manufacturing, transportation and related services such as banking. The Trust is
concentrated (i.e., invests 25% or more of Trust assets) in common stocks of companies within the industrials sector.&lt;/span&gt;&lt;/p&gt;

</fnd:NmRule35d1TermDfnTextBlock>
    <fnd:NmRule35d1TermSlctnCritTextBlock contextRef="AsOf2026-10-27" id="Fact000014">

&lt;p style="font: bold 11pt/11pt Times New Roman, Times, Serif; margin: 4pt 0 1pt"&gt;Portfolio Selection Process.&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt; text-indent: 0.25in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;The
stocks were selected for the Trust by Richard Bernstein Advisors using a comprehensive process and held for approximately two years.&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: -0.5in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;&lt;b&gt;&lt;i&gt;Step
1:&lt;/i&gt;&lt;/b&gt;	As of the date the portfolio was selected, Richard Bernstein Advisors starts with the Russell 2500&lt;sup&gt;TM &lt;/sup&gt;Index and
screens for industrial companies focused on infrastructure, manufacturing, transportation and related services such as banking. Banks
will be chosen from states considered traditional manufacturing hubs.&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: -0.5in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;&lt;b&gt;&lt;i&gt;Step
2:&lt;/i&gt;&lt;/b&gt;	Screen to exclude companies with non-U.S. sales greater than or equal to 25%.&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: -0.5in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;&lt;b&gt;&lt;i&gt;Step
3:&lt;/i&gt;&lt;/b&gt;	Positive 12-month forward earnings estimates. &lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: -0.5in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;&lt;b&gt;&lt;i&gt;Step
4:&lt;/i&gt;&lt;/b&gt;	Proprietary portfolio optimization method is used to weight the stocks. No position will exceed approximately 4% of the
total portfolio. Bank stocks will be limited to a maximum of approximately 10% of the portfolio.&lt;br/&gt;
Other portfolio criteria:&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: 0in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;-
$6 minimum share price;&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: 0in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;-
$200 million minimum market cap; and&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt 0.5in; text-indent: 0in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;-
liquidity of at least $500,000 trading volume on average each day.&lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt; text-indent: 0.25in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;While
not a part of the Trust&#x2019;s portfolio selection process, the Trust also invests in dividend paying securities. &lt;/span&gt;&lt;/p&gt;

&lt;p style="font: 10pt/11pt Times New Roman, Times, Serif; margin: 0 0 2pt; text-indent: 0.25in"&gt;&lt;span style="letter-spacing: -0.05pt"&gt;As
with any similar investments, there can be no guarantee that the objective of the Trust will be achieved. See &#x201c;Risk Factors&#x201d;
for a discussion of the risks of investing in the Trust.&lt;/span&gt;&lt;/p&gt;

</fnd:NmRule35d1TermSlctnCritTextBlock>
</xbrl>
