2006 Buick Rendezvous overheating.. fans come on, full coolant.

Hello, This tells me the water pump is not doing it's job, but try leaving it in park and raising the idle, does that make it get hot? If the water pump is working, driving should allow it to cool down, if the thermostat is bad, it will get hottest when parked. If there is a leak, it will overheat most times, but driving gently will cause it to stay cooler.