The net interest income itearns on these investment is the difference between the interest revenue on interest-earning assets and the interest expense incurred on interest-bearing liabilities.
Itearns revenues in form of interest on mortgage loans, production fee in writing new loans and service fee for servicing loans that it has sold to other parties.
American Express earns a net interest income on the spread between the rate itearns from un-loaned amounts sitting in bank deposits and short-term investments in financial securities and the rates at which it extends credit to card members.