Note 3 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Loans	$ 2,799,639,000	$ 2,753,085,000
Retail Portfolio Segment [Member]
Loans	399,441,000	392,979,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	83,127,000	85,439,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	316,314,000	307,540,000
Originated Loan [Member]
Loans	2,511,036,000	2,452,446,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	312,323,000	300,448,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	64,769,000	65,023,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	247,554,000	235,425,000
Acquired Loan [Member]
Loans	288,603,000	300,639,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	87,118,000	92,531,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	18,358,000	20,416,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 68,760,000	$ 72,115,000