Note 5 - Premises and Equipment - Components of Premises and Equipment (Details) (Parentheticals)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Building [Member] | Minimum [Member]
Useful lives (Year)	15 years	15 years
Building [Member] | Maximum [Member]
Useful lives (Year)	50 years	50 years
Furniture and Fixtures [Member] | Minimum [Member]
Useful lives (Year)	3 years	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Useful lives (Year)	10 years	10 years