The unit of currency in Indonesia is the Indonesian Rupiah (ID R). Most foreign exchange shops in Jakarta are located inside shopping malls, making it safe and convenient to change your currency. We were staying near Plaza Indonesia Shopping Mall so I exchanged currency at Dua Sisi Money Changer located in the mall’s basement level. You can refer to this Jakarta currency exchange guide to find a shop near you.
If you’d rather not bring too much foreign currency into Indonesia, then an alternative would be to withdraw ID R using an ATM. The rates are comparable, some say even better. Just be sure to advise your bank that you plan on using your ATM card abroad so you don’t run into any issues. In my experience, my card works in some machines but not in others.

NOTE: Some ATM’s will ask if you’d like to proceed “with or without conversion”. Always choose WITHOUT conversion. If you choose “with conversion”, then that allows the foreign bank operating the ATM to do the exchange, usually at terrible rates. The has happened to me and the difference in rates is shocking, in some cases up to 10%.