Note 3 - Loans and Allowance for Loan Losses - Retail Credit Exposure (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Loans	$ 2,554,272,000	$ 2,378,620,000
Retail Portfolio Segment [Member]
Loans	339,450,000	313,273,000
Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	103,376,000	118,047,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	236,074,000	195,226,000
Originated Loan [Member]
Loans	2,133,766,000	1,884,548,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Loans	210,768,000	155,650,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	69,325,000	69,831,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	141,443,000	85,819,000
Acquired Loan [Member]
Loans	420,506,000	494,072,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Loans	128,682,000	157,623,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
Loans	34,051,000	48,216,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Loans	$ 94,631,000	$ 109,407,000