Are mothers favored in child custody cases?

No.  Some Idaho case law acknowledges a presumption that primary custody with mother (especially during the early years) is presumed best.  But the Idaho Code (section 32-717) looks primarily at parental fitness, home stability, and other factors to determine which parenting schedule works best for the children.  This means that fathers can sometimes get primary custody, even over young children.  As children grow older, the Idaho Code presumes that frequent and meaningful contact with each parent is best, which means a significantly shared schedule.  These presumptions, however, are not binding on the courts, and cases may vary significantly depending on circumstances.