Note 16 - Financial Derivatives (Details Textual) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2014	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Junior Subordinated Notes, Total	$ 119,100
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ (793)	$ 1,666	$ (4,119)	$ 4,595
Cash [Member]
Collateral Already Posted, Aggregate Fair Value		9,100		9,100		$ 1,800
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative Outstanding, Notional Amount	$ 119,100	119,100		119,100		119,100
Derivative Original Maturity	10 years
Derivative, Average Fixed Interest Rate	2.61%
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax				4,400		241
Net Accrued on Interest Rate Swaps		$ 78	83	$ 41	480
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative, Average Variable Interest Rate		2.37%		2.37%
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative Outstanding, Notional Amount		$ 584,000		$ 584,000		613,400
Derivative, Average Fixed Interest Rate		4.71%		4.71%
Derivative, Average Variable Interest Rate		5.01%		5.01%
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax				$ (9,800)		6,600
Net Accrued on Interest Rate Swaps		$ 205	$ 96	$ 1,400	$ 132
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Minimum [Member]
Derivative Original Maturity				3 years
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Maximum [Member]
Derivative Original Maturity				10 years
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative, Basis Spread on Variable Rate		2.61%		2.61%
Negative Fair Value [Member]
Notional Amount Of Option Contract		$ 1,200		$ 1,200		1,200
Open Option Contracts Fair Value		6		6		6
Sum Of Spot And Forward Contract Notional Amount		121,800		121,800		95,000
Negative Fair Value		2,400		2,400		1,800
Positive Fair Value [Member]
Sum Of Spot And Forward Contract Notional Amount		71,000		71,000		86,900
Positive Fair Value		$ 965		$ 965		$ 397