new battery...high idle

[kwb210]

I installed a new battery. Actually bought a new one before the old one left me stranded...usually on a rainy night and certainly not near my home...upon starting the cold engine the idle steadied itself at 2500 rpm. It stayed there for a few minutes at the engine begin to warm. I did not drive anywhere, just idled. Eventually it came down to about 1200 when the temp stabilized at operating temperture acording to the gauge. Comments? Does the computer reset itself after I drive? Or is it the computer? We all know that once warm the idle is near 650. What is up?
Thanks!
Kurt
2000 tlc