Note 12 - Derivative Financial Instruments (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Junior Subordinated Notes, Total	$ 42,941	$ 41,849
Derivative Asset, Notional Amount	743,664	745,619
Short-term Debt, Total	441,500	441,500
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net, Total	200
Not Designated as Hedging Instrument [Member]
Derivative Asset, Notional Amount	36,300	36,300
Designated as Hedging Instrument [Member]
Derivative Asset, Notional Amount	265,800	267,800
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Asset, Notional Amount	441,500	441,500
Interest Rate Swap [Member]
Derivative Asset, Notional Amount	284,200	286,100
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Asset, Notional Amount	36,321	36,321
Floating Rate Junior Subordinated Debentures [Member]
Derivative, Amount of Hedged Item	18,000	18,000
Junior Subordinated Notes, Total	$ 61,900	$ 61,900