Note 5 - Investment Securities - Investment Securities by Contractual Maturity (Details) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Collateralized Mortgage Obligations [Member]
Available for Sale, No Specific Maturity Date, Amortized Cost	$ 150,708,000
Available for Sale, No Specific Maturity Date, Fair Value	152,866,000
Held to Maturity, No Specific Maturity Date, Amortized Cost	164,150,000
Held to Maturity, No Specific Maturity Date, Fair Value	167,638,000
Total, held to ,maturity, amortized cost	164,150,000	$ 146,458,000
Total, held to ,maturity, fair value	167,638,000	146,080,000
Collateralized Mortgage Backed Securities [Member]
Available for Sale, No Specific Maturity Date, Amortized Cost	9,357,000
Available for Sale, No Specific Maturity Date, Fair Value	9,419,000
Held to Maturity, No Specific Maturity Date, Amortized Cost	17,253,000
Held to Maturity, No Specific Maturity Date, Fair Value	17,643,000
Total, held to ,maturity, amortized cost	17,253,000	7,732,000
Total, held to ,maturity, fair value	17,643,000	7,711,000
Due in 1 year or less, available for sale, amortized cost	6,844,000
Due in 1 year or less, available for sale, fair value	6,861,000
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	16,065,000
After 1 year to 5 years, available for sale, fair value	15,694,000
After 1 year to 5 years, held to ,maturity, amortized cost	4,828,000
After 1 year to 5 years, held to ,maturity, fair value	4,817,000
After 5 years to 10 years, available for sale, amortized cost	45,375,000
After 5 years to 10 years, available for sale, fair value	44,290,000
After 5 years to 10 years, held to ,maturity, amortized cost	12,843,000
After 5 years to 10 years, held to ,maturity, fair value	13,088,000
After 10 years, available for sale, amortized cost	25,118,000
After 10 years, available for sale, fair value	24,159,000
After 10 years, held to ,maturity, amortized cost
After 10 years, held to ,maturity, fair value
Total, available for sale, amortized cost	253,467,000
Total, available for sale, fair value	253,289,000
Total, held to ,maturity, amortized cost	199,074,000	172,277,000
Total, held to ,maturity, fair value	$ 203,186,000	$ 171,845,000