If your laptop can't stand 100% CPU (and GPU) load for an indefinite time, you should consider it broken (or just very clogged up with dust). Anyway, it's very unlikely that Linux was persistently loading your system while it's supposed to be idle, so it's probably even more broken.
Or you could just read the laptop specs and see how they probably say "X GHz" and not "X GHz persistent load, Y GHz at peaks". Also look for things like "software has to downclock the CPU if it gets too hot". (btw, the Linux kernel does do that anyway for certain supported cpus, but this is just safety and not normal operation)
