Trigger the footable_expand_all event on the table to expand all detail rows:

$('table').trigger('footable_expand_all');

Trigger the footable_collapse_all event on the table to collapse all detail rows:

$('table').trigger('footable_collapse_all');

When using the paging add-on, you might want to trigger a redraw after you expand or collapse all detail rows, so that the paging is corrected:

$('table').trigger('footable_collapse_all').trigger('footable_redraw');