Ok, so I'm at the point in my chess where I understand memorizing openings isn't good - it's the ideas behind them that count. By ideas, I mean: the plans that each color should adopt (such as what pawn advances should be aimed for, what squares are each side trying to get control of) and what imbalances are each side aiming for. 

Reading through Silman's books, I understand that in each opening, white and black both have a plan they want to accomplish. If I know, say, what black is trying to accomplish when he does 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4, if white plays something unexpected, I won't be lost.

So I guess my question is, what positions are each side striving for in the top openings? I understand that's a lot of writing for one person to do in one post, so is there a book someone would recommend that explains each color's plans in the top openings? Does the ECO do this, or does it just have lots of continuations/variations?

Thanks!

That's a broad question.  Why not narrow it down to one opening at a time?

Check out http://www.thechesswebsite.com/chess-openings/index.php for some great introductory videos on various openings.

I also just picked up the Fundamental Chess Openings book and it seems to do a really good job of explaining ideas behind each opening without overloading you with variations 20 moves in.

I would recommend Reuben Fine's book, "Ideas Behind the Chess Openings."  The book was originally written in the 1950's I think, but Fine revised it in the early 1990's, so it includes most of today's popular openings.

Way too broad a question and you should absolutely get ''Mastering the Chess openings'' (volume 1 and 2) from John Watson explaining the main plans of almost every top opening except the English and the Dutch.