be
become
remain, stay
He never stayed idle for long.

bone (BrE,informal)
She never lifts a finger to help. She's bone idle.

be, lie, sit, stand
Half of their machines are lying idle.
The machines have been sitting idle since last year.
The pumps are standing idle.

become
He did not let the factory become idle.

remain
leave sth
The land was left idle for years.

Idle is used with these nouns:
banter, boast, chat, chatter, conversation, curiosity, gossip, talk, threat, time