Your scenario raises some potentially complicated issues. First off, you should review the effective custody/visitation orders so that you know the respective rights/obligations of the parties. Another important component is whether you have sole physical custody and legal custody. If you do, then that can weigh in your favor.
Determination of Custody/Visitation
There are numerous factors in play here. California courts must make custody orders that are in the best interest of the child. The order of preference is to grant joint custody to both parents (Fam. Code § 3040(a)). If that is not within the child's best interests, then the court prefers granting physical custody to the parent that would "allow the child frequent and continuing contact with the noncustodial parent" (Fam. Code § 3040(a)(1)). However, there are additional guidelines to this rule (see, e.g. Fam. Code § 3011). Sometimes a court will grant sole legal and physical custody depending on the factual circumstances (id.).
Primary Custodial Parent Moves Out of State
When it comes to moving out of state, that's a whole other matter. You must show that there has been a change in circumstances, and how the move will not detriment the child's best interest in frequent and ongoing contact with both parents (Fam. Code § 7501). Depending on the age of your child, the court may even consider his or her own opinion on the matter (Fam. Code § 3042(a)).
On the plus side, the father's distance and lack of contact for two years would weigh in your favor. This can show that the move would not be to the child's detriment because the frequency of contact would not be significantly altered. But you need to have good reasons for the move (i.e. guaranteed employment; better educational opportunities; or anything else that would result in a more favorable outcome for the child). On the other hand, if the move looks like an attempt to thwart the father/child relationship, the court will almost certainly not rule in your favor.
Noncustodial Parent's "Abandonment"
This presumption arises when a party seeks an order to terminate parental rights (see, Fam. Code §§ 7802, 7822). This means that the father would have no legal rights or obligations with respect to the child. In other words, he would no longer be the child's father. To obtain such an order, it must be shown by clear and convincing evidence that termination is in the best interest of the child. This is hard to do (unless there is child abuse; felonious conduct; etc.).
Also, this would mean that he is no longer required to make child support payments. And you would have no right to request any support orders, no matter how much circumstances have changed. It is a difficult and taxing process.
As shown above, you should consult with an attorney. And if you have decent enough relations with the father, you may want to just ask him to modify the custody agreement. One possibility is to offer covering some costs for the plane ticket to Idaho for any scheduled visits that are already set forth in the current visitation order. If he is okay with that, have an attorney draft the stipulation.
In the end, this is about the child. Not the parents' egos. If the move will make life better for the child, and if the father's rights won't be materially affected, you should consider working with him in a constructive manner to hash out a solid understanding. Then you can have an attorney prepare a stipulation to formalize the agreement. Another alternative would be to visit the Family Law Facilitator at your local courthouse to obtain their input, and see if they can help. Good luck; I hope a reasonable and non-confrontational result can be obtained.
***THE ABOVE IS STATED FOR INFORMATIONAL PURPOSES ONLY AND IS NOT LEGAL ADVICE. No attorney-client privilege applies to this general communication. Consultation with competent counsel is recommended.***
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