How to show Row details?

[Sergey]

Can someone point to the steps I have to make to Row details "+" indicator to appear?
What I have already is defined RowDetailsTemplate and bound ItemSource.
Looks like I'm missing something.

<telerik:RadGridView x:Name="GeoAuthGridView"
      ShowGroupPanel="False"
      AutoGenerateColumns="False"
      ItemsSource="{Binding GeoAuthorizations}">
 <telerik:RadGridView.Columns>
   <telerik:GridViewDataColumn Header="Designator"/>
   <telerik:GridViewDataColumn Header="Operator Name"/>
 </telerik:RadGridView.Columns>

 <telerik:RadGridView.RowDetailsTemplate>
  <DataTemplate>
   <StackPanel>
    <TextBlock Text="Item 1" />
    <TextBlock Text="Item 2" />
   </StackPanel>
  </DataTemplate>
 </telerik:RadGridView.RowDetailsTemplate>
</telerik:RadGridView>

Thank you.

[Sergey]

Got it!

Missing Column: <telerik:GridViewToggleRowDetailsColumn />

Thank you.