Idaho takes a strong stance against consensual sodomy between adults with 18-6605 which it calls "the infamous crime against nature". The penalty for a successful conviction is "not less than five years".
Married couples practicing sodomy in private may be constitutionally protected from being convicted of "the infamous crime against nature" after State v. Holden, 126 Idaho 755, 890 P.2d 341 (Ct. App. 1995).
Felatio is included as a banned act covered by the description of "the infamous crime against nature". [State v. Brashier, 127 Idaho 730, 905 P.2d 1039 (Ct. App. 1995)] [State v. Izatt, 96 Idaho 667, 534 P.2d 1107 (1975)]
Penetration is required as legally complete the act of sodomy by Idaho code section 18-6606.