sentences:  Excess insurance is similar in that it pays after an underlying primary policy is exhausted, but the critical difference is that excess policies are normally "follow form" policies that conform exactly to the coverage of the underlying policy, except that they add on their own excess limit which is then stacked on top of the primary policy's limit.Umbrella policies tend to provide broader coverage over one or more primary policies, in that they usually lack "follow form" clauses, their definitions of what is covered may be broader than the definitions in the primary policies, and they sometimes lack exclusions used in underlying primary policies.Thus, an umbrella policy may cover certain risks from the first dollar of loss or liability incurred, which were never covered under the primary policies.