Note 5 - Investment Securities - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Due in 1 year or less, available for sale, amortized cost	$ 650
Due in 1 year or less, available for sale, fair value	651
Due in 1 year or less, held to maturity, amortized cost
Due in 1 year or less, held to maturity, fair value
After 1 year to 5 years, available for sale, amortized cost	13,088
After 1 year to 5 years, available for sale, fair value	13,247
After 1 year to 5 years, held to maturity, amortized cost	4,408
After 1 year to 5 years, held to maturity, fair value	4,376
After 5 years to 10 years, available for sale, amortized cost	73,254
After 5 years to 10 years, available for sale, fair value	70,702
After 5 years to 10 years, held to maturity, amortized cost	93,789
After 5 years to 10 years, held to maturity, fair value	91,422
After 10 years, available for sale, amortized cost	25,471
After 10 years, available for sale, fair value	24,082
After 10 years, held to maturity, amortized cost
After 10 years, held to maturity, fair value
Total, available for sale, amortized cost	372,014
Total, available for sale, fair value	362,328
Total, held to maturity, amortized cost	421,850	$ 432,499
Total, held to maturity, fair value	413,699	425,183
Collateralized Mortgage Obligations [Member]
No specific maturity date, available for sale, amortized cost	222,278
No specific maturity date, available for sale, fair value	217,616
No specific maturity date, held to maturity, amortized cost	196,461
No specific maturity date, held to maturity, fair value	194,317
Total, held to maturity, amortized cost	196,461	202,990
Total, held to maturity, fair value	194,317	201,230
Collateralized Mortgage Backed Securities [Member]
No specific maturity date, available for sale, amortized cost	37,273
No specific maturity date, available for sale, fair value	36,030
No specific maturity date, held to maturity, amortized cost	127,192
No specific maturity date, held to maturity, fair value	123,584
Total, held to maturity, amortized cost	127,192	129,951
Total, held to maturity, fair value	$ 123,584	$ 126,625