Idaho Code § 70-1403: Quorum.

A majority of the persons holding the office of port commissioner at any time shall constitute a quorum of the port commission for the transaction of business, and the concurrence of a majority of the persons holding such office at the time shall be necessary and shall be sufficient for the transaction of any port business, but no business shall be transacted unless there are in office at least a majority of the full number of commissioners fixed by law.