IRS Form 990, "Return of Organization Exempt from Income Tax", is submitted by tax-exempt organizations. The Form 990 provides the public with financial information about a given organization.
The Foundation's 990s are available as pdf files:
2012 IRS 990 2011 IRS 990 2010 IRS 990 2009 IRS 990
2008 IRS 990 2007 IRS 990 2006 IRS 990 2005 IRS 990