Note 5 - Loans - Accruing Troubled Debt Restructurings (Details) - Accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accruing TDRs	$ 68,565	$ 65,393	$ 81,680	$ 104,356
Payment Deferral [Member]
Accruing TDRs	44,119	39,054
Contractual Interest Rate Reduction [Member]
Accruing TDRs	6,206	6,750
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	18,240	19,589
Commercial Portfolio Segment [Member]
Accruing TDRs	29,199	12,052
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	29,199	7,971
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Commercial Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs		4,081
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs	32,843	44,392
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	11,504	25,979
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,871	5,961
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	15,468	12,452
Residential Portfolio Segment [Member]
Accruing TDRs	6,523	8,949
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	3,416	5,104
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	335	789
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 2,772	$ 3,056