Note 9 - Income Taxes Summary of Income Tax Examinations (Details) - Internal Revenue Service (IRS) [Member] - USD ($) $ in Millions	Jun. 30, 2017	Sep. 04, 2014	May 31, 2010	Jun. 30, 2008
Income Tax Examination [Line Items]
Income Tax Examination, Amount of Claimed Income Tax Refund Being Disallowed for Tax Years 2006 and 2007		$ 105
REMIC Residual [Member]
Income Tax Examination [Line Items]
Qualified Deposit With The U.S. Department Of Treasury Relating to Tax Years 2000 Through 2004				$ 85
Qualified Deposit With The U.S. Department Of Treasury Relating To Tax Years 2005 Through 2007			$ 4
Income Tax Examination, Penalties Accrued		$ 157
Income Tax Examination, Notice of Deficiency, Amounts Related to Unpaid Taxes and Penalties	$ 143
Income Tax Examination, Proposed State Liabilities Resulting from IRS Examination of Tax Years 2000 Through 2007	$ 36