Note 8 - Loans - Accruing Troubled Debt Restructurings (Details) - 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	$ 62,358	$ 79,819	$ 65,393	$ 86,555	$ 74,708	$ 81,680
Payment Deferral [Member]
Accruing TDRs	48,542		39,054
Contractual Interest Rate Reduction [Member]
Accruing TDRs	6,232		6,750
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	7,584		19,589
Commercial Portfolio Segment [Member]
Accruing TDRs	21,416		12,052
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	21,416		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
Real Estate Construction Loans [Member]
Accruing TDRs	7,480
Real Estate Construction Loans [Member] | Payment Deferral [Member]
Accruing TDRs	7,480
Real Estate Construction Loans [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Real Estate Construction Loans [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs	26,812		44,392
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	16,130		25,979
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,895		5,961
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	4,787		12,452
Residential Portfolio Segment [Member]
Accruing TDRs	6,650		8,949
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	3,516		5,104
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	337		789
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 2,797		$ 3,056