When conducting a follow-up review for a paper you already made comments on, how detailed should the review be? I think the title stands on its own, but I am not sure how detailed to make follow-up reviewer comments for a paper.  My sense is that I don't need to re-review the paper, but just comment on whether or not I am satisfied with the changes the authors made.  This leaves a rather skimpy review the second time around.
The extent of a re-review depends on what has been done with the manuscript (MS). If the first review round yielded questions and comments that can be fixed but may require checking to make sure the implementation of the comments are correct, then, as you say, you will not have to do a full-blown re-review. If, on the other hand, the revisions are such that the MS has been substantially modified, perhaps with new parts added, new data included, etc. the situation is different. Then the paper is so modified it is in some way more of a new MS than just revised and, hence in need of a new throrough review.

So in my opinion, the need of re-review depends on the severity of the required changes. How you decide depends on your opinion of the new paper. If an editor feels a MS is in need of so substantial revisions it becomes a new MS, then it is often rejected with a note about re-submission after work has been done. So in the end it is your view of the severity or magnitude of necessary changes that largely determines how much should be done. In some cases authors may disagree with a comment you feel strongly about and in such cases it may be necessary to enforce the view through more careful and convincing scrutiny.

EDIT: I should perhaps add that a second or more reviewers may have given other comments that influence your review. This means parts of the MS can be changed in ways you have not suggested so although a new detalied re-review may not be necessary a careful read through and comparison with the old may be in order. Sometimes authors (we) can use conflicting reviews to argue against one or the other.