I reject idealism, which I suspect is the Mahayana view, too. Realism and idealism are both wrong. I spent like 20 years on this issue. There is no lasting “mind” for idealism to be correct. All there is is namarupa…a series of mind-moments and their content, but the delusion that the mind-moments are one, continuous mind is, well, a delusion. The delusion that the contents of those mind-moments exist outside the citta is also a delusion. Citta and contents arise together as one mind-moment.
As far as I can tell, this is consistent with Abhidhamma. Realism is just the default view and thus what people are very inclined to “read into” their interpretations. That’s all. That’s my take on it.