If for some reason, you do not want to use module (*.iml) references for your IDEA project, you can choose to do so using:
mvn idea:idea -DlinkModules=false
or in your pom.xml:
<project>
[...]
<build>
[...]
<plugins>
[...]
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-idea-plugin</artifactId>
<version>2.2.1</version>
<configuration>
<linkModules>false</linkModules>
</configuration>
</plugin>
[...]
</plugins>
[...]
</build>
[...]
</project>