olistic endeavor," and because "[a] provision that may seem ambiguous in isolation is often clarified by the remainder of the statutory scheme," It a United Sam. Ass'n of Tex. a Timbers of Inwood Forest Assocs., Ltd., 484 U.S. 365, 371, 108 S.Ct. 626, 98 L.Ed.2d 740 (1988), we first examine the balance of