Best Way to script Mecanim Animation CrossFade?

I want to script a shooting animation.

There are two animations for t$$anonymous$$s w$$anonymous$$ch is Idle and Fire.

T$$anonymous$$s is my script:

 var PlayerAnimator : Animator
 
 if(Input.GetMouseButtonDown(1))
 {
    PlayerAnimator.CrossFade("Fire",1);
 }
 else 
 {
    PlayerAnimator.CrossFade("Idle",1);
 }

I am also a bit unsure about the Crossfade as in how the value will affect the transition.