You are professionally responsible for the state of construction documents you've produced with your stamp and signature at the time you leave the company. Though it is at the discretion of the company, they should allow you to keep a copy for your records. Any changes made to your drawings by a new E.O.R. that takes over is the responsibility of the new E.O.R. For this reason alone, the company should let you keep a copy.
I'm not aware of any legal rights but if the drawings you stamped and signed contain company's standard details and so on, it is unethical to reuse them for projects at your new company. Then again, many "content" of structural typical details are essentially code based which can not be copyrighted, thus you may generate your own details "based" on some of these details.
Copying and pasting your previous firm's CAD details on your future company's projects (regardless whether you reviewed the content) could result in a lawsuit.