Note 2 - Investment Securities - Continuous Unrealized Loss Position (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Continuous unrealized loss, greater than 12 months, gross unrealized losses	$ (3,749)	$ (4,213)
Continuous unrealized loss, fair value	280,473	285,171
Continuous unrealized loss, gross unrealized losses	(6,275)	(7,703)
Continuous unrealized loss, less than 12 months, fair value	172,188	177,689
Continuous unrealized loss, less than 12 months, gross unrealized losses	(2,526)	(3,490)
Continuous unrealized loss, greater than 12 months, fair value	108,285	107,482
US Government Agencies Debt Securities [Member]
Continuous unrealized loss, greater than 12 months, gross unrealized losses	(3,749)	(4,213)
Continuous unrealized loss, fair value	278,697	281,683
Continuous unrealized loss, gross unrealized losses	(6,248)	(7,673)
Continuous unrealized loss, less than 12 months, fair value	170,412	174,201
Continuous unrealized loss, less than 12 months, gross unrealized losses	(2,499)	(3,460)
Continuous unrealized loss, greater than 12 months, fair value	108,285	107,482
US States and Political Subdivisions Debt Securities [Member]
Continuous unrealized loss, greater than 12 months, gross unrealized losses
Continuous unrealized loss, fair value	1,776	3,488
Continuous unrealized loss, gross unrealized losses	(27)	(30)
Continuous unrealized loss, less than 12 months, fair value	1,776	3,488
Continuous unrealized loss, less than 12 months, gross unrealized losses	(27)	(30)
Continuous unrealized loss, greater than 12 months, fair value