Fly-Out Menu background

I have enabled the fly-out menu option on my SharePoint 2013 master page using the code below.  Can someone tell me how to set the width of the background box?  In Chrome the text is wider than the box, and in IE the box is really tall and narrow, and it wraps the text for each of my links to 8 or 10 lines.  Thanks.  

<SharePoint:AspMenu
id="V4QuickLaunchMenu"
runat="server"
EnableViewState="false"
DataSourceId="QuickLaunchSiteMap"
UseSimpleRendering="true"
Orientation="Vertical"
StaticDisplayLevels="1"
         ItemWrap="false"
AdjustForShowStartingNode="true"
MaximumDynamicDisplayLevels="1"
         StaticSubMenuIndent="0"
SkipLinkText=""
/>