I'm in the maxing out stage of my Town Hall 8 village, which means I don't use elixir much, and I have full elixir storages all the time, with a capacity of 6,000,000 elixir (3 level 11 storages).
According to the wiki, level 11 elixir storages give 10% of their current resources when destroyed during an attack. There is a maximum cap for amount of elixir stolen from storages, which is 450,000 elixir.
However, most of the times when my village gets completely destroyed, 3-star raid, the amount of elixir stolen is only about 350,000. This is way less than the maximum cap or 10% of the resources, and I'm not even taking into account collectors, the Town Hall and the Clan Castle.