To me, this is probably the most stupid solution that Germany (or any other country) could have come up with. The banks will pay what is effectively an insurance premium, paid into a bailout fund which will be called upon in the event they need financial assistance later. (Unfortunately, in reality it's more likely it will just end up in the Chancellor's tax slush fund and used to pay welfare recipients or something, like all the other taxes. A bailout will still end up really being paid by taxpayers if/when it occcurs.)
So, the banks will be allowed to take risks as before, but now they will have contributed to some limited extent to their bailout fund when it all blows up next time. I tell you this (even if this money is indeed kept somewhere in escrow for the time it is needed), I very much doubt that the "insurance fund" they will have paid into will be anywhere close to big enough to cover the cost of bailing them out -- the lion's share will almost certainly still, in my opinion, be contributed by taxpayers.
Better solutions would have involved curtailment of certain bank activities and/or splitting their commercial and retail banking operations from their proprietary trading (gambling) operations, to reduce the risk of failures or at least to render them no-longer-too-big-to-fail. All this insurance fund will do is partially mitigate the problem, when it will occur. (The government would not require an insurance premium, if its plans somehow were going to credibly remove that risk.) It is like a green light for the banks to enjoy Business As Usual, but with a small insurance premium penalty.
It will probably convince a lot of voters that the banks are getting punished by politicians though, which is convenient...