Note 8 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Accruing TDRs	$ 33,691	$ 30,045	$ 29,722	$ 20,870	$ 25,442	$ 39,923
Payment Deferral [Member]
Accruing TDRs	15,320		17,431
Contractual Interest Rate Reduction [Member]
Accruing TDRs	1,706		1,795
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	16,665		10,496
Commercial Portfolio Segment [Member]
Accruing TDRs	13,259		14,565
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	13,259		14,565
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Commercial Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs	19,561		14,633
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,347		2,510
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	1,706		1,795
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	16,508		10,328
Residential Portfolio Segment [Member]
Accruing TDRs	871		524
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	714		356
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 157		$ 168