Yeah - you allow engine temps to come up by driving the car, albeit gently until it reaches normal operating temps! Think about what your are trying to achieve by letting the car idle without driving it - you want to get it to operating temp asap; but by trying it that way, you are ensuring that the motor spends much longer running BELOW normal operating temp - exactly what you want to avoid, since that is what can cause wear.
To warm it up quickly and properly, start the car and drive away promptly. Don't rev hard or use heavy throttle until the needle's where it should be.
