If you just type in "system idle process explained" in a search engine it'll bring up posts explaining what it means.

System Idle Process explained...
http://forum.osnn.net/showpost.php?p=13824&postcount=1

I get the impression it's typical, but I might also be wrong as I'm not quite awake.

If I click on Task Manager, it's the CPU percentage is fluctuating heaps. In fact when I first click TAsk Manager and I'm not doing anything else, it goes immediately to CPU usage 100% then slides down to 30% and then fluctuates at lower percentages.