Excess (slightly difference from Umbrella Insurance) has become the more common option over Umbrella.

This provides coverage for losses in excess of your underlying liability insurance limits and is a “following form Excess Liability policy following the 'scheduled' underlying policy's terms and conditions subject to the excess carriers terms and conditions."

Which in layman's terms means it only increases the limits of what is covered in your primary or underlying insurance, it does not fill in gaps of coverage or cover additional items not already covered.