need help Animation script

Im trying to add a idle Animation Butt wen i do it just overrides the other animation

function Update () {

var forward = Input.GetKey(KeyCode.W);
var run = Input.GetKey(KeyCode.LeftShift) && (KeyCode.W);

if(forward){
	animation.CrossFade("walk");
	transform.Translate(0 ,0 , Input.GetAxis("Vertical") * 0.10);
}
if(run){
	animation.CrossFade("run");
	transform.Translate(0 ,0 , Input.GetAxis("Vertical") * 0.20);
}
else{
animation.CrossFade("idle");
}

}

You are missing an “else” in front of if(run) so if you are not running, you are idling.