Expandable textarea width in stylesheet

My textarea is very small and I use a 2 col style site. It would be really nice to be able to expand the the textarea width for creating content to fill the rest of the page.
Currently this is what drupal shouts out loud when rendering the page

<div class="form-item">
 <label for="edit-default-message">Default message text: </label>
 <textarea cols="70" rows="10" name="default_message" id="edit-default-message"  class="form-textarea resizable"></textarea>
</div>