The conformation and scaling properties of self-avoiding fluid membranes with an extrinsic bending rigidity kappa were studied with the use of Monte Carlo methods. For kappa = 0, the results are consistent with branched polymer behavior at large length scales. There is a smooth crossover from a crumpled to an extended state with increasing kappa, with a peak in the specific heat when the persistence length reaches the system size. The scale-dependent effective bending rigidity is a decreasing function of system size for all bare rigidities. These results indicate that fluid membranes are always crumpled at sufficiently long length scales.