The Collaborative International Dictionary of English v.0.48:

nonpartisanship \nonpartisanship\ n.
   An inclination to weigh both views or opinions equally;
   absence of bias toward any particular party.

   Syn: impartiality.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonpartisanship
    n 1: an inclination to weigh both views or opinions equally
         [syn: impartiality, nonpartisanship] [ant:
         partiality, partisanship]