Note 17 - Fair Value Measurements and Fair Values of Financial Instruments (Details Textual)	12 Months Ended
	Dec. 31, 2017 USD ($) security issuer	Dec. 31, 2016 USD ($)
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Number of underlying issuers | issuer	5
Expected credit losses or prepayments	$ 0
Swap rate period	30 years
Discount rate	6.00%
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	$ 15,000	$ 0
Fair Value, Inputs, Level 3 [Member] | Collateralized Debt Obligations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Number Of Trust Preferred Securities | security	1
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	$ 15,000	$ 0