Twelve Coins, Unknown Direction

You have 12 coins that look identical. Exactly one is counterfeit and has a different weight from the rest, but you do NOT know whether it is heavier or lighter. Using only a two-pan balance scale (each weighing reports left-heavy, right-heavy, or balanced), what is the minimum number of weighings that guarantees you both identify the counterfeit AND determine whether it is heavy or light? Weighings may be chosen adaptively.