Note 5 - Investment Securities - Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months	$ 57,856	[1]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(6,521)	[1]
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
Debt Securities, Unrealized Loss Position	57,856
Debt Securities, Unrealized Loss Position, Accumulated Loss	(6,521)
CLO III Subordinated Notes [Member]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months	10,580	[1]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,697)	[1]
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
Debt Securities, Unrealized Loss Position	10,580
Debt Securities, Unrealized Loss Position, Accumulated Loss	(1,697)
CLO IV Junior Subordinated Notes [Member]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months	23,297	[1]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,877)	[1]
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
Debt Securities, Unrealized Loss Position	23,297
Debt Securities, Unrealized Loss Position, Accumulated Loss	(2,877)
CLO V Junior Subordinated Notes [Member]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months	23,979	[1]
Debt Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,947)	[1]
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer
Debt Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
Debt Securities, Unrealized Loss Position	23,979
Debt Securities, Unrealized Loss Position, Accumulated Loss	$ (1,947)

[1] For all CLO debt securities, the gross unrealized loss is measured since the date of deconsolidation, which was January 17, 2019 for CLO III and March 19, 2019 for CLO IV and CLO V.