● IB will sell your stocks if your margin reach the limits it sets. I guess that your broker account is insured, including IB's, up to a limit, say, 1 million, or 100K.
○ AFAIK, it is 1 million.
○ They are not insured by insurance companies such as AIG. Just like your bank account, your bank contributes money to a fund managed by an organization. Your broker also contributes money to the insurance fund.