I'm looking at my pg_stat_activity and trying to figure out what is causing some of these processes. I'm using this query:
SELECT pid, wait_event, state_change, backend_start, xact_start, query_start, state_change - query_start, query from pg_stat_activity where datname= 'my_database' and state in ('idle', 'idle in transaction', 'idle in transaction (aborted)', 'disabled');
Including the "state" field should clear things up considerably.