Note 4 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans	$ 2,753,085,000	$ 2,558,552,000
Retail Portfolio Segment [Member]
Loans	392,979,000	354,984,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	85,439,000	100,425,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	307,540,000	254,559,000
Originated Loan [Member]
Loans	2,452,446,000	2,169,957,000	$ 1,884,548,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	300,448,000	235,729,000	$ 155,650,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	65,023,000	69,675,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	235,425,000	166,054,000
Acquired Loan [Member]
Loans	300,639,000	388,595,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	92,531,000	119,255,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	20,416,000	30,750,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 72,115,000	$ 88,505,000