Note 15 - Financial Derivatives (Details Textual) - USD ($)		3 Months Ended		6 Months Ended
	May 31, 2014	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Junior Subordinated Notes, Total	$ 119,100,000
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ 736,000	$ (550,000)	$ 2,929,000	$ (251,000)
Cash [Member]
Collateral Already Posted, Aggregate Fair Value		361,000		361,000		$ 4,500,000
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative Outstanding, Notional Amount	$ 119,100,000	119,100,000		119,100,000
Derivative Original Maturity	10 years
Derivative, Average Fixed Interest Rate	2.61%
Derivative, Average Variable Interest Rate	2.33%
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax				1,200,000	(2,400,000)
Net Accrued on Interest Rate Swaps		123,000	439,000	396,000	900,000
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative Outstanding, Notional Amount		$ 631,400,000	446,100,000	$ 631,400,000	446,100,000
Derivative, Average Fixed Interest Rate		4.70%		4.70%
Derivative, Average Variable Interest Rate		4.70%		4.70%
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax				$ 13,000,000	1,000,000
Net Accrued on Interest Rate Swaps		$ 0	$ 651,000	229,000	$ 1,400,000
Derivative, Notional Amount at Origination		$ 631,400,000		$ 631,400,000
Derivative, Average Basis Spread on Variable Rate		271.00%		271.00%
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Minimum [Member]
Derivative Original Maturity				2 years
Interest Rate Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Maximum [Member]
Derivative Original Maturity				10 years
Negative Fair Value [Member]
Notional Amount Of Option Contract		$ 1,700,000		$ 1,700,000		1,000,000
Open Option Contracts Fair Value		9,000		9,000		9,000
Sum Of Spot And Forward Contract Notional Amount		92,700,000		92,700,000		32,100,000
Negative Fair Value		2,100,000		2,100,000		453,000
Positive Fair Value [Member]
Sum Of Spot And Forward Contract Notional Amount		62,700,000		62,700,000		108,500,000
Positive Fair Value		$ 389,000		$ 389,000		$ 1,800,000