Note 15 - Fair Value of Financial Instruments - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Held to maturity securities	$ 42,446	$ 25,090
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Cash and cash equivalents	80,571	78,789
Securities sold under agreement to repurchase	21,629	19,114
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	80,571	78,789
Securities sold under agreement to repurchase	21,629	19,114
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Held to maturity securities	42,879	26,977
Interest-bearing time deposits in banks	4,075	4,571
Other investment securities	24,802	13,759
Loans held for sale	7,258	8,954
Cash surrender value of life insurance	57,794	57,267
Accrued interest receivable	8,027	7,006
Checking, money market and savings accounts	1,103,047	1,095,178
Other borrowings	372,316	152,004
Accrued interest payable	640	314
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Held to maturity securities	42,446	25,090
Interest-bearing time deposits in banks	4,095	4,572
Other investment securities	24,802	13,759
Loans held for sale	7,258	8,954
Cash surrender value of life insurance	57,794	57,267
Accrued interest receivable	8,027	7,006
Checking, money market and savings accounts	1,103,047	1,095,178
Other borrowings	372,124	151,605
Accrued interest payable	640	314
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans receivable—net	1,692,463	1,540,805
Certificates of deposit	486,089	548,902
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans receivable—net	1,696,254	1,551,099
Certificates of deposit	$ 484,958	$ 548,520