Idling as such isn't bad for an engine - it's wasteful because it burns
gas without providing movement, but you needn't worry about your
engine's health when it has to sit idling for a couple minutes.

Two exceptions:

If your car has a pulley driven fan and you've driven it hard in hot
weather, putting it idling may cause the water temperature to shoot up
because the fan doesn't turn quick enough in idle. In these
circumstances it'll be better to drive at a more leisurely pace for the
last couple minutes, so the engine can cool off with the help of the
wind.

Idling a cold engine causes a lot of wear. Actually everything done with
a cold engine causes a lot of wear, so to minimize it one should aim to
bring an engine to operating temperature as quick as possible with the
minimum damage. The best compromise is driving the car without pushing
it, giving the engine medium load.

Idling, optimized for minimal load, will take ages to warm the engine.
In cold weather it may actually not warm up at all. Starting a cold
engine it is probably best to give it a couple seconds idle - while
putting on the seat belt - so oil pressure is built up. Then drive it.

cu
 .\\arc

mostly it just wastes gas.

That said, some motors have some parts that are splash or drip oiled and
may not get enough oil at idle.

For example, the lobes on a small block chevy's cam are not pressure
lubed, which is why you need to rev it up on a new cam install - there's
not enough oil pressure (and not enough drippage) to properly lube a new
cam.  So, long idling periods in a small block chevy would probably
accelerate wear on the cam... but probably nothing you'd notice until a
lot of miles anyway.

but, mostly it just wastes gas.

Ray