Why do I have the "required reviews completed" status on my submission in Elsevier?
To expand on Dirk's comment: The status you see means that the reviewers have submitted their reports to the online system, and the handling editor has received an email about this. Now she has to read the  comments (and likely look at your manuscript again to see if they comments are relevant), come to a decision, and write a corresponding letter to the author summarizing the comments and justifying the decision. This will in general not take more than an hour. 

But you should keep in mind that yours is not the only manuscript (nor, in all likelihood, the only journal) the editor has to deal with. In addition, this is both the end of semester and conference season in many parts of the world, so it is reasonable to assume that the editor is just very busy with more urgent deadlines, or isn't even in office. (Remember, editors are unpaid, so this work is on top of the regular duties of teaching, advising and doing their own research.)
In some cases, the final decision even involves two editors (associate/managing editor and editor-in-chief/communicating editor), which doubles the chance of other things getting in the way. 

In light of that, I would say two weeks is definitely too early to worry and start contacting the editor; give it at least a month. 

(Although I know how stressful the wait at this stage of the publication process is...)