When a user is logged in to his Google account, the search terms of this user are not displayed in Google Analytics. Even if a user is logged in to one of Google’s other tools (Google+, Analytics, Webmaster Tools), the search behavior is not recorded. This logged-in visitor uses the Google search function via a secure connection (HTTPS). You will therefore not see the search term for logged-in visitors. Instead, it says “not provided”.
Knowledge base glossary