Created Unassigned: Can't override Floating Document and Anchorable style [17760]

Hi,

I'm trying to override styles for Floating Document and Anchorable but I can't.

For document, I edited style, based it on the initial style and then modified the background for example (even if I want to modify the control template later) but at the end nothing changes.

I did this:
<Style x:Key="{x:Type xcad:LayoutDocumentFloatingWindowControl}" TargetType="{x:Type xcad:LayoutDocumentFloatingWindowControl}" BasedOn="{StaticResource {x:Type xcad:LayoutDocumentFloatingWindowControl}}" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
__<Setter Property="Background" Value="Red" />__
</Style>

Same thing without key.

Thanks in advance for your help