arm's length

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A distance approximately equal to the length of a human's arm.
• noun figuratively A position not suggesting or inviting intimacy.
• noun figuratively A condition of independence and parity for parties to a transaction.
• adjective literally Barely within reach.
• adjective idiomatic Distant, detached.
• adjective idiomatic Independent, but related.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a distance sufficient to exclude intimacy