After a report is run, rows can have either a "-" or a "+" symbol to denote an available action to either expand or collapse the account details to reveal or hide the data.
On some reports, a Row/Grid Format needs to be selected to activate this feature.
Alternatively, on some reports you can also "Right-Click" in the results grid and choose to either "Expand All" or "Collapse All" to display or hide all rows for all accounts.
(Collapse All status pictured above)
(Expand All status pictured above)