Note 3 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Loans	$ 2,881,493,000	$ 2,753,085,000
Retail Portfolio Segment [Member]
Loans	416,938,000	392,979,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	81,320,000	85,439,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	335,618,000	307,540,000
Originated Loan [Member]
Loans	2,609,686,000	2,452,446,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	334,755,000	300,448,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	64,247,000	65,023,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	270,508,000	235,425,000
Acquired Loan [Member]
Loans	271,807,000	300,639,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	82,183,000	92,531,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	17,073,000	20,416,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 65,110,000	$ 72,115,000