The Collaborative International Dictionary of English v.0.48:

levelheaded \lev"el*head"ed\ a.
   exercising or showing good judgment or common sense;
   sensible.

   Syn: healthy, intelligent, sound.
        [WordNet 1.5] -- lev"el*head"ed*ly, adv. --
        lev"el*head"ed*ness, n.
        [PJC]