I have already checked this post: How to download dependency sources for Gradle project in IDEA?
But it didn\'t work for me. Maybe it is because they are referring t
Unfortunately I cannot comment with my score, so:
Although this isn't an answer, if you use the 'eclipse' plugin in Gradle, you can run
gradle eclipseClasspath
And it will download all the sources and, I believe, Javadoc and create a .classpath with links to their locations.
Then, at least, you will have the sources and javadoc to reference, which I assume you can then reference in IntelliJ.