Note 10 - Derivative Financial Instruments (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Junior Subordinated Notes	$ 36,071		$ 36,071		$ 33,959
Derivative Asset, Notional Amount	347,503		347,503		253,414
Short-term Debt	50,000		50,000
Derivative, Net Hedge Ineffectiveness Gain (Loss)	0	$ 0	0	$ 0
Not Designated as Hedging Instrument [Member]
Derivative Asset, Notional Amount	36,300		36,300		36,300
Designated as Hedging Instrument [Member]
Derivative Asset, Notional Amount	261,200		261,200		217,100
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Asset, Notional Amount	50,000		50,000		0
Interest Rate Swap [Member]
Derivative Asset, Notional Amount	279,500		279,500		235,400
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Asset, Notional Amount	50,000		50,000
Floating Rate Junior Subordinated Debentures [Member]
Derivative, Amount of Hedged Item	18,000		18,000		18,000
Junior Subordinated Notes	$ 61,900		$ 61,900		$ 61,900