<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>322</ContextCount>
  <ElementCount>210</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>140</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>2</UnitCount>
  <MyReports>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>01001 - Document - Document and Entity Information {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/DocumentAndEntityInformation1</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory></MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>01002 - Document - Risk/Return Summary (MainStay Winslow Large Cap Growth Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary2</Role>
      <ShortName>Risk/Return Summary (MainStay Winslow Large Cap Growth Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>01003 - Disclosure - Risk/Return Detail Data (MainStay Winslow Large Cap Growth Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData3</Role>
      <ShortName>Risk/Return Detail Data (MainStay Winslow Large Cap Growth Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>01010 - Document - Risk/Return Summary (MainStay MacKay International Equity Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary10</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay International Equity Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>01011 - Disclosure - Risk/Return Detail Data (MainStay MacKay International Equity Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData11</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay International Equity Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>01018 - Document - Risk/Return Summary (MainStay Winslow Large Cap Growth Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary18</Role>
      <ShortName>Risk/Return Summary (MainStay Winslow Large Cap Growth Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>01019 - Disclosure - Risk/Return Detail Data (MainStay Winslow Large Cap Growth Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData19</Role>
      <ShortName>Risk/Return Detail Data (MainStay Winslow Large Cap Growth Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>01026 - Document - Risk/Return Summary (MainStay MacKay International Equity Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary26</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay International Equity Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>01027 - Disclosure - Risk/Return Detail Data (MainStay MacKay International Equity Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData27</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay International Equity Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>01034 - Document - Risk/Return Summary (MainStay Candriam Emerging Markets Debt Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary34</Role>
      <ShortName>Risk/Return Summary (MainStay Candriam Emerging Markets Debt Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>01035 - Disclosure - Risk/Return Detail Data (MainStay Candriam Emerging Markets Debt Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData35</Role>
      <ShortName>Risk/Return Detail Data (MainStay Candriam Emerging Markets Debt Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>01042 - Document - Risk/Return Summary (MainStay MacKay High Yield Corporate Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary42</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay High Yield Corporate Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>01043 - Disclosure - Risk/Return Detail Data (MainStay MacKay High Yield Corporate Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData43</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay High Yield Corporate Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>01050 - Document - Risk/Return Summary (MainStay MacKay Strategic Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary50</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay Strategic Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>01051 - Disclosure - Risk/Return Detail Data (MainStay MacKay Strategic Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData51</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay Strategic Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>01058 - Document - Risk/Return Summary (MainStay MacKay U.S. Infrastructure Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary58</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay U.S. Infrastructure Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>01059 - Disclosure - Risk/Return Detail Data (MainStay MacKay U.S. Infrastructure Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData59</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay U.S. Infrastructure Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>01066 - Document - Risk/Return Summary (MainStay MacKay Tax Free Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary66</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay Tax Free Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>01067 - Disclosure - Risk/Return Detail Data (MainStay MacKay Tax Free Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData67</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay Tax Free Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>01074 - Document - Risk/Return Summary (MainStay Money Market Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary74</Role>
      <ShortName>Risk/Return Summary (MainStay Money Market Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>01075 - Disclosure - Risk/Return Detail Data (MainStay Money Market Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData75</Role>
      <ShortName>Risk/Return Detail Data (MainStay Money Market Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>01082 - Document - Risk/Return Summary (MainStay Income Builder Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary82</Role>
      <ShortName>Risk/Return Summary (MainStay Income Builder Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>01083 - Disclosure - Risk/Return Detail Data (MainStay Income Builder Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData83</Role>
      <ShortName>Risk/Return Detail Data (MainStay Income Builder Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>01090 - Document - Risk/Return Summary (MainStay MacKay Convertible Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary90</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay Convertible Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>01091 - Disclosure - Risk/Return Detail Data (MainStay MacKay Convertible Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData91</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay Convertible Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>01098 - Document - Risk/Return Summary (MainStay Candriam Emerging Markets Debt Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary98</Role>
      <ShortName>Risk/Return Summary (MainStay Candriam Emerging Markets Debt Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>01099 - Disclosure - Risk/Return Detail Data (MainStay Candriam Emerging Markets Debt Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData99</Role>
      <ShortName>Risk/Return Detail Data (MainStay Candriam Emerging Markets Debt Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>01106 - Document - Risk/Return Summary (MainStay MacKay High Yield Corporate Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary106</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay High Yield Corporate Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>01107 - Disclosure - Risk/Return Detail Data (MainStay MacKay High Yield Corporate Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData107</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay High Yield Corporate Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>01114 - Document - Risk/Return Summary (MainStay MacKay Strategic Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary114</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay Strategic Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>01115 - Disclosure - Risk/Return Detail Data (MainStay MacKay Strategic Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData115</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay Strategic Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R122.htm</HtmlFileName>
      <LongName>01122 - Document - Risk/Return Summary (MainStay MacKay U.S. Infrastructure Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary122</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay U.S. Infrastructure Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>01123 - Disclosure - Risk/Return Detail Data (MainStay MacKay U.S. Infrastructure Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData123</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay U.S. Infrastructure Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>01130 - Document - Risk/Return Summary (MainStay MacKay Tax Free Bond Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary130</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay Tax Free Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R131.htm</HtmlFileName>
      <LongName>01131 - Disclosure - Risk/Return Detail Data (MainStay MacKay Tax Free Bond Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData131</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay Tax Free Bond Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R138.htm</HtmlFileName>
      <LongName>01138 - Document - Risk/Return Summary (MainStay Money Market Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary138</Role>
      <ShortName>Risk/Return Summary (MainStay Money Market Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R139.htm</HtmlFileName>
      <LongName>01139 - Disclosure - Risk/Return Detail Data (MainStay Money Market Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData139</Role>
      <ShortName>Risk/Return Detail Data (MainStay Money Market Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R146.htm</HtmlFileName>
      <LongName>01146 - Document - Risk/Return Summary (MainStay Income Builder Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary146</Role>
      <ShortName>Risk/Return Summary (MainStay Income Builder Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R147.htm</HtmlFileName>
      <LongName>01147 - Disclosure - Risk/Return Detail Data (MainStay Income Builder Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData147</Role>
      <ShortName>Risk/Return Detail Data (MainStay Income Builder Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R154.htm</HtmlFileName>
      <LongName>01154 - Document - Risk/Return Summary (MainStay MacKay Convertible Fund) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRSummary154</Role>
      <ShortName>Risk/Return Summary (MainStay MacKay Convertible Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R155.htm</HtmlFileName>
      <LongName>01155 - Disclosure - Risk/Return Detail Data (MainStay MacKay Convertible Fund) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.mainstayinvestments.com/20211031/role/RRDetailData155</Role>
      <ShortName>Risk/Return Detail Data (MainStay MacKay Convertible Fund)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>41</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="485BPOS" original="c485bpos.htm">c485bpos.htm</File>
    <File>c485bpos-20220225.xsd</File>
    <File>c485bpos-20220225_cal.xml</File>
    <File>c485bpos-20220225_def.xml</File>
    <File>c485bpos-20220225_lab.xml</File>
    <File>c485bpos-20220225_pre.xml</File>
    <File>ex99ilegalopinin-1.htm</File>
    <File>ex99jotheropinin-1.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>img_0374629aef584f4.jpg</File>
    <File>img_05bb48e104ac4f4.jpg</File>
    <File>img_07205767453e4f5.jpg</File>
    <File>img_0a7469368dc14f3.jpg</File>
    <File>img_11c094095c9d4f3.jpg</File>
    <File>img_18d0bb7c29ea4f5.jpg</File>
    <File>img_19f8cbb657d54f2.jpg</File>
    <File>img_1b566a1b12e54f5.jpg</File>
    <File>img_1e7492e8ede44f4.jpg</File>
    <File>img_22cc989176d34f4.jpg</File>
    <File>img_2577c96f3aa54f5.jpg</File>
    <File>img_39916c9337c54f4.jpg</File>
    <File>img_43020dc636ec4f3.jpg</File>
    <File>img_4cc3d5d64c164f5.jpg</File>
    <File>img_4f0c96d7931b4f4.jpg</File>
    <File>img_506debb5bf044f4.jpg</File>
    <File>img_50ca74d843b84f5.jpg</File>
    <File>img_525e069471474f3.jpg</File>
    <File>img_54e30073d96d4f3.jpg</File>
    <File>img_59068158dcfe4f4.jpg</File>
    <File>img_68f37b4f03204f3.jpg</File>
    <File>img_694b57f0740a4f2.jpg</File>
    <File>img_6d2ccbb296074f5.jpg</File>
    <File>img_6eb220f494944f4.jpg</File>
    <File>img_7110774339d64f4.jpg</File>
    <File>img_71c3a939ab064f5.jpg</File>
    <File>img_725cd03743e24f2.jpg</File>
    <File>img_7947174a12fe4f5.jpg</File>
    <File>img_7ae8c03550ac4f5.jpg</File>
    <File>img_84b056fcf75c4f2.jpg</File>
    <File>img_8500383d21024f4.jpg</File>
    <File>img_887d2c43c9b14f4.jpg</File>
    <File>img_89c3ff5dfe5c4f4.jpg</File>
    <File>img_8abcc62fee2c4f2.jpg</File>
    <File>img_8ce79a59b97b4f2.jpg</File>
    <File>img_9849953bca3d4f2.jpg</File>
    <File>img_9c220102b0db4f4.jpg</File>
    <File>img_b6e0c2a60d904f4.jpg</File>
    <File>img_b9d9e16ce0574f4.jpg</File>
    <File>img_cad2ebe543734f2.jpg</File>
    <File>img_cc65bbb8b2bb4f3.jpg</File>
    <File>img_ce936332e3df4f5.jpg</File>
    <File>img_d0322814d8384f3.jpg</File>
    <File>img_d951738b93194f3.jpg</File>
    <File>img_d9e73fc547a04f2.jpg</File>
    <File>img_ddb623104c7f4f4.jpg</File>
    <File>img_df829394677b4f2.jpg</File>
    <File>img_e0b8500f654e4f5.jpg</File>
    <File>img_ecc9d7390a074f5.jpg</File>
    <File>img_ee975800d0c34f3.jpg</File>
    <File>img_f667f41d620b4f5.jpg</File>
    <File>img_f89c770581f44f5.jpg</File>
    <File>img_fd27247cf8b34f5.jpg</File>
    <File>img_fff9f39c976c4f5.jpg</File>
    <File>BarChart1.png</File>
    <File>BarChart2.png</File>
    <File>BarChart3.png</File>
    <File>BarChart4.png</File>
    <File>BarChart5.png</File>
    <File>BarChart6.png</File>
    <File>BarChart7.png</File>
    <File>BarChart8.png</File>
    <File>BarChart9.png</File>
    <File>BarChart10.png</File>
    <File>BarChart11.png</File>
    <File>BarChart12.png</File>
    <File>BarChart13.png</File>
    <File>BarChart14.png</File>
    <File>BarChart15.png</File>
    <File>BarChart16.png</File>
    <File>BarChart17.png</File>
    <File>BarChart18.png</File>
    <File>BarChart19.png</File>
    <File>BarChart20.png</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="158">http://xbrl.sec.gov/dei/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy items="4127">http://xbrl.sec.gov/rr/2018-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
