Note 9 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale	$ 158,002	$ 159,320
Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	158,002	159,320
Fair Value, Recurring [Member] \| Interest Rate Swap [Member]
Interest rate swaps	43
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Rate Swap [Member]
Interest rate swaps	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	158,002	159,320
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Interest rate swaps	43
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Interest rate swaps	0
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Available-for-sale	110,009	125,678
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	110,009	125,678
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0	0
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	110,009	125,678
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0	0
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Debt Securities, Available-for-sale	5,416
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	5,416
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale	0
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	5,416
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale	0
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale	42,577	33,642
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member]
Debt Securities, Available-for-sale	42,577	33,642
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale	$ 42,577	$ 33,642