What does 2 Kings 23:12 mean?

He tore down the altars the kings of Judah had built on the roof near Ahaz’s upstairs room, as well as the altars Manasseh had made in the two courtyards of the Lord’s temple. He smashed them to pieces and threw the rubble into the Kidron Valley. 2 Kings 23:12 - Modern Text Bible

(Josiah destroys every trace of idol worship, even the altars built by previous kings, making sure nothing is left.)