If you're on Linux, run this as your first command in IDLE:

    import pydoc; pydoc.pager = lambda text: pydoc.tempfilepager(pydoc.plain(text), 'xterm -e less')

If Windows: 

    import pydoc; pydoc.pager = lambda text: pydoc.tempfilepager(pydoc.plain(text), 'notepad')

All help() output for objects will now display outside of IDLE.

The Squeezer extension does something similar for output that is longer than 30 lines.

It should be possible to create a custom pager for the subprocess which communicates with IDLE to display this text. RPCProxy could be used to accomplish this in conjunction with the textView module.