p:dialog don'nt show buttons when maximize - primefaces

Question

I have the next issue with a p:dialog in a xhtml. In this p:dialog I have 3 buttons in the bottom of the dialog. The code is:
<p:dialog header="window" minimizable="true" maximizable="true" width="800" height="500" modal="true">
<p:outputPanel>
<p:panelGrid columns="1">
<p:dataGrid columns="1" var="var" layout="grid">
<p:panel style="text-align: justify;">
<f:facet name="header">
<h:outputText value="##{fila + 1}"/>
<p:outputPanel style="float:right;">
<h:outputText value="reter"/>
<h:outputText value="fdsfds" >
<f:convertDateTime pattern="dd/MM/yyyy HH:mm:ss" />
</h:outputText>
</p:outputPanel>
</f:facet>
<p:panelGrid columns="1" >
<h:outputText value="gefdgdf" />
</p:panelGrid>
</p:panel>
</p:dataGrid>
<p:row>
<br/>
<p:column>
<h:outputText value="gdfgdf" />
</p:column>
</p:row>
</p:panelGrid>
</p:outputPanel>
<f:facet name="footer">
<p:outputPanel style="float:right;">
<p:commandLink >
<i class="fa fa-comment-o fa-2x"/>
</p:commandLink>
<p:commandLink >
<i class="fa fa-floppy-o fa-2x"/>
</p:commandLink>
<p:commandLink >
<i class="fa fa-pencil fa-2x"/>
</p:commandLink>
</p:outputPanel>
</f:facet>
</p:dialog>
When I maximize the dialog, the buttons (f:facet name="footer") don't show it. Why?