Note 5 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accruing TDRs	$ 33,416	$ 29,722	$ 39,923	$ 41,618
Payment Deferral [Member]
Accruing TDRs	20,472	17,431
Contractual Interest Rate Reduction [Member]
Accruing TDRs	1,677	1,795
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	11,267	10,496
Commercial Portfolio Segment [Member]
Accruing TDRs	12,944	14,565
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	12,944	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	19,021	14,633
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	6,231	2,510
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	1,677	1,795
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	11,113	10,328
Residential Portfolio Segment [Member]
Accruing TDRs	1,451	524
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,297	356
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 154	$ 168