Mecanim Periodic Animation

Hi, when my character stands still, I want to play an idle animation when character remains idle 30 seconds. I also want to have more than one animation to random in-between. Let's say in one character pokes his nose, in another it looks around itself.

I could not figure a way to take the time parameter from the last time I entered idle state. If I had that, I could change states according to it.

Please help.