From the Expedia website:
"What documentation will I need at check-in If I have bought an E-Ticket?
You can proceed directly to check-in, you will not need to collect your ticket at the ticketing desk. At check-in you will be asked for your Passport (you can use a photo ID for domestic flights) and you will be issued with your boarding card
Alternatively you can check-in at the Self Service check-in machines. These will ask for your credit card, frequent flyer card or passport to verify your name. This is a fast and convenient way to check-in, particularly if you only have hand luggage. If you have luggage to check-in, then you may still be able to use the machines but you would need to give your luggage to the airline before going to the departure lounge. Most e-ticket airlines will have a 'baggage drop' counter, but if in doubt, please ask an airline representative"
Chris