After importing the project into IntelliJ for the first time I ran into an issue where IDEA was unable to resolve dependencies from the Scala SDK added by SBT.
I managed to find a workaround that I'll post below in case anyone else is running into the same problem. I tested this using IntelliJ 14.0.3 and Scala plugin version 1.3.2.
1. Open project settings and add a new Global Library (Scala SDK)
2. Choose version 2.10.4 from your local Ivy repository
3. Add the new SDK to all modules
4. Move the new global Scala SDK above the one included by SBT
Now rebuild the project and IntelliJ should be able to resolve all dependencies in the Scala SDK.