I would like to efile my state return (Idaho) but paper file my federal return. How do I do that?

You can't do that.   You can't e-file a state return unless you e-file the federal return.   See this help article.  

Why do you want to paper file the Federal return?   If you are due a Federal refund, that will delay it by several weeks.    Are you getting an efile rejection notice?   If so, provide the rejection error code/message, and someone here in the forum may be able to offer a suggestion on how to fix it and efile.