Is this a bad idle or motor mounts?

Visually inspect the motor mounts. It's usually pretty obvious when they are bad because they will be cracked or torn. Could also be a loose motor mount bolt but I wouldn't think there is something wrong with the engine if the RPM's are staying steady. Another way to check would be to pop the hood and give it gas through the accelerator cable. If the motor jerks when you give it gas then you've found your culprit.