In St. Paul Fire & Marine Insurance Co. v. Gilmore, 168 Ariz. 159, 812 P.2d 977 (1991), the Arizona Supreme Court discussed the two respects in which insurance may be deemed excess: (1) "true excess" coverage, which provides coverage for a modest premium against catastrophic losses that exceed the limits of the underlying coverage; (2) when other insureds have purchased insurance that fortuitously may be applicable to a given loss. Id. at 162-63, 812 P.2d at 980-81.