Note 6 - Agency Securities, Available for Sale (Detail) - Gross Unrealized Losses and Estimated Fair Value of Agency Securities (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value
Less than 12 months	$ 7,175,317	$ 1,521,052
12 Months or More	17,737	836
Total	7,193,054	1,521,888
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Less than 12 months	(197,536)	(12,030)
12 Months or More	(292)	(3)
Total	$ (197,828)	$ (12,033)