Note 4 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans	$ 2,856,667,000	$ 2,753,085,000
Retail Portfolio Segment [Member]
Loans	415,123,000	392,979,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	75,374,000	85,439,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	339,749,000	307,540,000
Originated Loan [Member]
Loans	2,614,725,000	2,452,446,000	$ 2,169,957,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	343,308,000	300,448,000	$ 235,729,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	61,060,000	65,023,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	282,248,000	235,425,000
Acquired Loan [Member]
Loans	241,942,000	300,639,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	71,815,000	92,531,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	14,314,000	20,416,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 57,501,000	$ 72,115,000