Note 8 - Loans - Portfolio by Risk Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Loans	$ 12,597,434	$ 11,201,275
Loans held for sale		7,500
Commercial Portfolio Segment [Member]
Loans	2,419,891	2,248,187
Real Estate Construction Portfolio Segment [Member]
Loans	691,486	548,088
Commercial Real Estate Portfolio Segment [Member]
Loans	6,377,047	5,785,248
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	3,104,288	2,615,759
Consumer Portfolio Segment [Member]
Loans	4,722	3,993
Pass [Member]
Loans	11,794,042	10,513,473
Loans held for sale
Pass [Member] | Commercial Portfolio Segment [Member]
Loans	2,216,816	2,023,114
Pass [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	604,363	469,909
Pass [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	5,904,023	5,410,623
Pass [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	3,064,118	2,605,834
Pass [Member] | Consumer Portfolio Segment [Member]
Loans	4,722	3,993
Special Mention [Member]
Loans	549,639	435,032
Loans held for sale
Special Mention [Member] | Commercial Portfolio Segment [Member]
Loans	146,479	140,682
Special Mention [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	65,375	44,129
Special Mention [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	305,927	250,221
Special Mention [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	31,858
Special Mention [Member] | Consumer Portfolio Segment [Member]
Loans
Substandard [Member]
Loans	253,722	252,672
Loans held for sale		7,500
Substandard [Member] | Commercial Portfolio Segment [Member]
Loans	56,565	84,293
Substandard [Member] | Real Estate Construction Portfolio Segment [Member]
Loans	21,748	34,050
Substandard [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans	167,097	124,404
Substandard [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	8,312	9,925
Substandard [Member] | Consumer Portfolio Segment [Member]
Loans
Doubtful [Member]
Loans	31	98
Loans held for sale
Doubtful [Member] | Commercial Portfolio Segment [Member]
Loans	31	98
Doubtful [Member] | Real Estate Construction Portfolio Segment [Member]
Loans
Doubtful [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans
Doubtful [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans
Doubtful [Member] | Consumer Portfolio Segment [Member]
Loans