Excess vs. Umbrella
Excess insurance is similar to Umbrella insurance in that it responds after an underlying primary policy is exhausted. The major difference is that Excess policies are typically "follow form" and follow exactly the coverages of the underlying policy, except 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 typically lack "follow form" clauses. Their definitions of what is covered may be broader than the definitions in the primary policies, and may sometimes lack exclusions used in underlying primary policies. With this in mind, an Umbrella policy may cover certain insured perils from the “first dollar of loss”, which were never previously covered under the primary policies. However, an Umbrella policy may include what is called a Drop Down Exclusion, which eliminates coverage, for those perils that are left uncovered by the primary policies.