The odds of a commercial bank going bust is higher then Germany going bust. Commercial banks only need to keep a few % of the money deposited at them on their books (its called fractional reserve banking), the other 95% or so can be invested or lent out elsewhere. There are regulations that restrict the risk, require hedging, insurance, etc but those don't help much if the insurer or a significant amount of the borrowers go bust as well due to systemic problems.