You should file an Idaho tax return because nonresidents must file if their gross income from Idaho sources is more than $2500. However, since you have a net loss, you most likely won't pay any tax.
In TurboTax, in the Personal Info section, indicate that you made money in another state. Then, just file your rental income on the federal side, the program will carry the information to the Idaho tax return. File your nonresident state first, then CA.
