IDAHO is callsign for aircraft supporting the US Customs service (But not the USCS). More than likely an FBI helo. OMAHA is the USCS callsign.
The other call sign you're hearing is "Med-fly". There's a bunch of King-Airs dropping sterilized med-flies to control the fruit fly population.
There's also Ameriflight, a freight company, and if you slur their callsign "AMFLIGHT" on the radio it also sounds alot like "med-flight".
--Carlos V.