Mainly the Homeowner’s association (see early article at http://www.rawstory.com/rs/2012/04/09/zimmermans-homeowners-association-could-owe-millions-in-martin-case/ ). That’s the deep pocket most closely tied as having acknowledged and will be purported to have condoned all his activity. While they should fight it and win, insurance companies for the association will likely settle if the thugs parents don’t get too greedy. It’s all about weighing the risk - how much will it cost to defend and what are the odds of losing - and how much.
I believe the insurance company for the homeowners association has already paid a settlement to the family. That was a very fast and quiet civil case, and the amount involved was about $1.5M if I remember correctly.