Note 3 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Loans	$ 2,636,856,000	$ 2,558,552,000
Retail Portfolio Segment [Member]
Loans	374,886,000	354,984,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	91,229,000	100,425,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	283,657,000	254,559,000
Originated Loan [Member]
Loans	2,296,204,000	2,169,957,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	269,011,000	235,729,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	66,683,000	69,675,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	202,328,000	166,054,000
Acquired Loan [Member]
Loans	340,652,000	388,595,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	105,875,000	119,255,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	24,546,000	30,750,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 81,329,000	$ 88,505,000