Note 4 - Fair Value Measurements - Continuous Unrealized Loss Positions (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Held-to-maturity and available-for-sale, fair value, less than 12 months	$ 66,640
Held-to-maturity and available-for-sale, gross unrealized loss, less than 12 months	(1,566)
Held-to-maturity and available-for-sale, fair value, greater than 12 months
Held-to-maturity and available-for-sale, gross unrealized loss, greater than 12 months
Held-to-maturity and available-for-sale, fair value	66,640
Held-to-maturity and available-for-sale, gross unrealized loss	(1,566)
CLO III [Member]
Held-to-maturity, fair value, less than 12 months	13,122
Held-to-maturity, gross unrealized loss, less than 12 months	(511)
Held-to-maturity, fair value, greater than 12 months
Held-to-maturity, gross unrealized loss, greater than 12 months
Held-to-maturity, fair value	13,122
Held-to-maturity, gross unrealized loss	(511)
CLO IV [Member]
Available-for-sale, fair value, less than 12 months	27,262
Available-for-sale, gross unrealized loss, less than 12 months	(660)
Available-for-sale, fair value, greater than 12 months
Available-for-sale, gross unrealized loss, greater than 12 months
Available-for-sale, fair value	27,262
Available-for-sale, gross unrealized loss	(660)
CLO V [Member]
Available-for-sale, fair value, less than 12 months	26,256
Available-for-sale, gross unrealized loss, less than 12 months	(395)
Available-for-sale, fair value, greater than 12 months
Available-for-sale, gross unrealized loss, greater than 12 months
Available-for-sale, fair value	26,256
Available-for-sale, gross unrealized loss	$ (395)