Note 8 - Loans - Accruing Troubled Debt Restructurings (Details) - Accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Accruing TDRs	$ 74,598	$ 84,487	$ 68,565	$ 62,358	$ 79,819	$ 65,393
Payment Deferral [Member]
Accruing TDRs	44,834		44,119
Contractual Interest Rate Reduction [Member]
Accruing TDRs	7,775		6,206
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	21,989		18,240
Commercial Portfolio Segment [Member]
Accruing TDRs	27,153		29,199
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	27,153		29,199
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	41,262		32,843
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	14,248		11,504
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	7,446		5,871
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	19,568		15,468
Residential Portfolio Segment [Member]
Accruing TDRs	6,183		6,523
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	3,433		3,416
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	329		335
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 2,421		$ 2,772