Note 7 - Fair Value Measurement (Details) - Fair Value of Financial Assets and Liabililties Measure on Recurring Basis - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets:
Available-for-sale securities	$ 54,757	$ 52,544
US Government Agencies Debt Securities [Member]
Assets:
Available-for-sale securities	28,738	26,436
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Assets:
Available-for-sale securities	8,373	8,773
US States and Political Subdivisions Debt Securities [Member]
Assets:
Available-for-sale securities	17,646	17,335
Fair Value, Inputs, Level 2 [Member]
Assets:
Available-for-sale securities	54,757	52,544
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Assets:
Available-for-sale securities	28,738	26,436
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Assets:
Available-for-sale securities	8,373	8,773
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets:
Available-for-sale securities	$ 17,646	$ 17,335