I have a travel voucher from American Airlines. Can I use part of it now, and the rest later?

Last month, I was bumped and received a $400 travel voucher from American Airlines, in the form of a printed paper voucher (not an eVoucher, which Google tells me exists and plays by different rules). Can I use my voucher to book a flight that costs, say $200, and use the remaining balance towards another seperate booking?

If so, can I do so at a later date in a seperate transaction? Or do I need to spend the voucher all at once, regardless of whether it is on one or more distinct itineraries?