It's in their annual report:

http://phx.corporate-ir.net/External.File?item=UGFyZW50SUQ9M...

See page 24(29) where they list annual revenue for past five years:

  2004 - 6.0B
  2003 - 5.9B
  2002 - 5.6B
  2001 - 5.2B
  2000 - 5.0B

EDIT: Your statement about no real business doing $0 in revenue kept on nagging me. So I went and looked up their 2010 10k. They actually did $3.2B in 2010. So this chart is NOT accurate. They did do $4.0B in 2009, but only dropped to $3.2B in 2010.

Just because you file for bankruptcy doesn't mean you have zero revenue.