It's getting to be with windows, there really isn't much of what we used to think of as idle. Generally that was a pc at rest, no user input or programs running and @ 5% or less cpu usage. But shortly after that state happens, windows starts doing background stuff and usage continuously bounces upto @ 50% usage. Up until the point where windows timers say it's time for the pc to go into sleep modes, at which point wattage used drops from @ 100ish or more, to well below that. But thats sleep, not idle.
35°C when the pc is doing nothing is about normal. Case temps generally run @ 6-12°C above ambient (your room), so the cpu will be slightly above that.