Note 3 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Loans	$ 2,551,204,000	$ 2,558,552,000
Retail Portfolio Segment [Member]
Loans	358,175,000	354,984,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	93,179,000	100,425,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	264,996,000	254,559,000
Originated Loan [Member]
Loans	2,191,851,000	2,169,957,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	244,885,000	235,729,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	65,604,000	69,675,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	179,281,000	166,054,000
Acquired Loan [Member]
Loans	359,353,000	388,595,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	113,290,000	119,255,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	27,575,000	30,750,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 85,715,000	$ 88,505,000