The best way to compare row details in table

What is the best solution to represent more details in tables?

What is this page about.
This page contains logs (history of changes) for some rules. Imagine that admin set up a rule and then another admin modified the rule. There could be many modifications made by different admins. All the modifications will be reflected in the table. We show "when" the rule was modified, "who" modified and details ("what exactly" was modified). What is the best way to show those details if we don't have enough space in the table?

Note: User wants to compare details from one row to another.