A plug for isolating a wellbore. The plug can include a body having a first end and a second end, at least one malleable element disposed about the body, at least one slip disposed about the body, at least one conical member disposed about the body, and an insert secured to an inner surface of the body proximate the second end of the body. The insert can be adapted to receive a setting tool that enters the body through the first end thereof. The insert can include a passageway extending therethrough. The insert can be adapted to release the setting tool when exposed to a predetermined axial force, thereby providing a flow passage through the insert and the body. At least one of the body and the insert can be adapted to receive an impediment that restricts fluid flow in at least one direction through the body, wherein the impediment comprises one or more decomposable materials.