The USLI umbrella policy states: “If you are legally liable to pay damages for a loss to which this insurance applies, we will pay your net loss in excess of the retained limit. … We are not, however, obligated to defend any claim or suit which is covered in whole or in part by other insurance available to you, whether or not designated as primary, excess or contingent; provided, however, this shall not apply to insurance written specifically as excess coverage over this policy.” The policy defines the retained limit as the greater of the minimum underlying limits, the limit set forth on the schedule of underlying insurance, or the actual limit of underlying insurance available for injury or damage, without reduction for defense costs, court costs, investigation expenses, interest, or other costs.