To generate the files needed for an IntelliJ IDEA Project setup, you only need to execute the main plugin goal, which is idea:idea like so:
mvn idea:idea
The above command will execute the other three goals needed to setup your project for IntelliJ IDEA: idea:project, idea:module, and idea:workspace.
Please note that this plugin has no way to determine the name of the JDK you are using. By default, this uses the JDK name equivalent to java -version in your machine. If you know the name of the JDK to use, for example, 1.5, you can then execute:
mvn idea:idea -DjdkName=1.5