Laravel 5 sync() on pivot table

I want to sync pivot table in lavarel 5. When I create document, everything is fine, but when I want to update I get mysql error.

code with sync()

    if($document->update(array('id' => $request->id, 'name' => $request->name))) {
        $doc_ids = $request->documentation_appliance;

        $document->appliances()->sync($doc_ids);
    }

and I get this error

QueryException in Connection.php line 651:
SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'documentation_id' cannot be null (SQL: insert into `appliances_documentation` (`appliances_id`, `documentation_id`) values (6, ))

I though sync() will do everything, attach and detach, but seems like I am wrong. Can anyone tell me please a correct way how to do this? Thank you

via Chebli Mohamed