Wordpress theme addition to add the page's slug, and the page's oldest ancestor's slug to the body class. Very useful for hierarchies.

functions.php

function get_top_level_page() {
    global $top_level_page;
	global $post;
	// Get global page heading
	if( is_page() && !$top_level_page) {
		/* Get an array of Ancestors and Parents if they exist */
		$parents = get_post_ancestors( $post->ID );
			/* Get the top Level page->ID count base 1, array base 0 so -1 */
		if($parents) {
			$id = $parents[count($parents)-1];
		}
		else {
			$id = $post->ID;
		}
		/* Get the parent and set the $class with the page slug (post_name) */
		$top_level_page = get_page( $id );
	}
}
add_action('wp_head', 'get_top_level_page');


// Add post slug to body class
function add_body_class( $classes )
{
    global $post;
    if ( isset( $post ) ) {
        $classes[] = $post->post_type . '-' . $post->post_name;
    }
    if( is_page() ) {
    	get_top_level_page();
    	global $top_level_page;
    	if($top_level_page) {
			$classes[] = $post->post_type . '-' . $top_level_page->post_name;
		}
    }
    return $classes;
}
add_filter( 'body_class', 'add_body_class' );