protected function _get_detail_page_url( $user_id ) {
		$detail_keys = $this->_add_detail_url_field();
		$detail_keys = array_keys( $detail_keys );
		foreach ( $detail_keys as $key ) {
			$detail_url = get_the_author_meta( $key, $user_id );
			if ( $detail_url ) {
				return $detail_url;
			}
		}
	}