Note 12 - Derivative Financial Instruments - Derivative Financial Instruments (Details) - USD ($)		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Interest rate swaps, notional amount		$ 841,690,000		$ 745,619,000
Interest rate swaps, net carrying value	[1]	(18,512,000)		13,722,000
Designated as Hedging Instrument [Member]
Interest rate swaps, notional amount		263,900,000		267,800,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Interest rate swaps, notional amount		541,500,000	$ 441,500,000
Not Designated as Hedging Instrument [Member]
Interest rate swaps, notional amount		36,300,000		36,300,000
Interest Rate Swaps 1 [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Interest rate swaps, notional amount		80,835,000		248,330,000
Interest rate swaps, net carrying value	[1]	1,635,000		10,593,000
Interest Rate Swaps 1 [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Interest rate swaps, notional amount		0		441,500,000
Interest rate swaps, net carrying value	[1]	0		5,368,000
Interest Rate Swaps 2 [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Interest rate swaps, notional amount		183,034,000		19,468,000
Interest rate swaps, net carrying value	[1]	(6,886,000)		(502,000)
Interest Rate Swaps 2 [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Interest rate swaps, notional amount		541,500,000		0
Interest rate swaps, net carrying value	[1]	(8,878,000)		0
Interest Rate Swap [Member]
Interest rate swaps, notional amount		282,200,000		286,100,000
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Interest rate swaps, notional amount		36,321,000		36,321,000
Interest rate swaps, net carrying value	[1]	$ (4,383,000)		$ (1,737,000)

[1] Derivatives in a positive position are recorded as "Other assets" and derivatives in a negative position are recorded as "Other liabilities" in the Consolidated Statements of Financial Condition.