How to find the actual space being consumed by indexes on a table in Oracle?

How to find the actual space being consumed by indexes on a table in Oracle?

SELECT idx.index_name, SUM(bytes)
  FROM dba_segments seg,
       dba_indexes  idx
 WHERE idx.table_owner = <<owner of table>>
   AND idx.table_name  = <<name of table>>
   AND idx.owner       = seg.owner
   AND idx.index_name  = seg.segment_name
 GROUP BY idx.index_name