SplitWindow Adding Content to Detail Window?

Ok, so I have a navigation group in the master window, works as expected. Once the final navigation is tapped, I am creating a controller and I want to add or open a window in the detail view of the splitwindow.

<SplitWindow platform="ios" formFactor="tablet">
 
                    <!-- The 'masterView' window, added via <Require> tag -->
                    <Window>
 
                        <NavigationGroup  id="menu_navigation_group">
 
                            <Require src="folder/menu" nav="top_level"/>
                        </NavigationGroup>
 
                    </Window>
 
                    <!-- The 'detailView' window,-->
                    <Window id="builder_detail">
                        <Label>I am Window 1</Label>
                    </Window>
 
                </SplitWindow>

I'm using this code to try to open another controller and view in the detail

in the folder/menu controller

var anotherController = Alloy.createController('builder/detail_view', nav);
Alloy.Globals.builder_detail.open(anotherController.getView());

Nothing is erring, but nothing is happening in the detail view..... Any guidance as to where I'm going wrong?