Note 9 - Income Taxes Summary of Income Tax Examinations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Sep. 04, 2014	May 31, 2010	Jun. 30, 2008
Income Tax Examination [Line Items]
Income Tax Expense (Benefit)	$ (28,378)	$ (8,132)	$ (422)	$ 30,066
Income Tax Expense (Benefit) Recorded as a Result of Finalized IRS Settlement	(73,600)
Qualified Deposit Assets With The U.S. Department Of Treasury Expected to be Submitted	31,000		31,000
Deposit Assets	$ 88,557		88,557		$ 88,557
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities			$ 88,600
Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Income Tax Examination, Amount of Claimed Income Tax Refund Being Disallowed for Tax Years 2006 and 2007						$ 105,000
REMIC Residual [Member] | Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Qualified Deposit With The U.S. Department Of Treasury Relating to Tax Years 2000 Through 2004								$ 85,000
Qualified Deposit With The U.S. Department Of Treasury Relating To Tax Years 2005 Through 2007							$ 4,000
Income Tax Examination, Penalties Accrued						$ 157,000