What is the relationship between curse Oedipus lays upon murder and statement that he speak idle words?

Oedipus curses the killer of Laius, saying he will be banished and "live in pain where ever you stay." Then he says he speaks "ille words." The second statement is ironic, because Oedipus curse is not idle at all. It comes true, and Oedipus himself ended up fulfilling it.